How to auto fill lines in the selection

I'm sure that there must be a more elegant way of dealing with this, however, this brute force approach appears to work in a quick test. Please let me know how it works for you!

// create separations for four point paths;
// 2020, use it at your own risk;
if (app.documents.length > 0) {
    var thePathIndex = selectedPath2020();
    if (thePathIndex != -1) {
        var originalRulerUnits = app.preferences.rulerUnits;
        app.preferences.rulerUnits = Units.PIXELS;
        var thePath = collectPathInfoFromDesc2020(activeDocument, thePathIndex);
        // if path has one subpathitem and four points;
        if (thePath.length == 1 && thePath[0].length == 6) {

            ////////////////////////////////////
            // Capture the original resolution ppi value
            var origRes = app.activeDocument.resolution;
            // Set the resolution to 72 ppi without resampling
            app.activeDocument.resizeImage(null, null, 72, ResampleMethod.NONE);
            ////////////////////////////////////
            // Original input
            var sep1input = prompt("Enter the number across:", 3);
            // Remove anything that is not a digit or full point
            var sep1inputCleaner = sep1input.replace(/[^\d\.]/, '');
            // Convert to integer
            var sep1toDigit = parseInt(sep1inputCleaner, 10);
            // Final result
            var sep1 = sep1toDigit;
            // Original input
            var sep2input = prompt("Enter the number down:", 7);
            // Remove anything that is not a digit or full point
            var sep2inputCleaner = sep2input.replace(/[^\d\.]/, '');
            // Convert to integer
            var sep2toDigit = parseInt(sep2inputCleaner, 10);
            // Final result
            var sep2 = sep2toDigit;
            ////////////////////////////////////
            var point1 = thePath[0][0][0];
            var point2 = thePath[0][1][0];
            var point3 = thePath[0][2][0];
            var point4 = thePath[0][3][0];
            var theArray2 = new Array;
            theArray2.push(thePath[0]);
            ////////////////////////////////////
            var theDistH1 = (point2[0] - point1[0]) / (sep1 + 1);
            var theDistV1 = (point2[1] - point1[1]) / (sep1 + 1);
            var theDistH2 = (point4[0] - point3[0]) / (sep1 + 1);
            var theDistV2 = (point4[1] - point3[1]) / (sep1 + 1);
            for (var m = 1; m <= sep1; m++) {
                var point1a = [point1[0] + m * theDistH1, point1[1] + m * theDistV1];
                var point2a = [point4[0] - m * theDistH2, point4[1] - m * theDistV2];
                theArray2.push([
                    [point1a, point1a, point1a, false],
                    [point2a, point2a, point2a, false], false, 1807
                ])
            };
            ////////////////////////////////////
            var theDistH1 = (point3[0] - point2[0]) / (sep2 + 1);
            var theDistV1 = (point3[1] - point2[1]) / (sep2 + 1);
            var theDistH2 = (point1[0] - point4[0]) / (sep2 + 1);
            var theDistV2 = (point1[1] - point4[1]) / (sep2 + 1);
            for (var m = 1; m <= sep2; m++) {
                var point1a = [point2[0] + m * theDistH1, point2[1] + m * theDistV1];
                var point2a = [point1[0] - m * theDistH2, point1[1] - m * theDistV2];
                theArray2.push([
                    [point1a, point1a, point1a, false],
                    [point2a, point2a, point2a, false], false, 1807
                ])
            };
            ////////////////////////////////////
            var thePath = createPath2018(theArray2, Math.random());
            app.preferences.rulerUnits = originalRulerUnits;
            strokeLayer(String(sep1 + "x" + sep2));
            thePath.remove();
            ////////////////////////////////////
            // Reset the original resolution without resampling
            app.activeDocument.resizeImage(null, null, origRes, ResampleMethod.NONE);
        }
    };
};
////// collect path info from actiondescriptor, smooth added //////
function collectPathInfoFromDesc2020(myDocument, thePath) {
    var originalRulerUnits = app.preferences.rulerUnits;
    app.preferences.rulerUnits = Units.PIXELS;
    // based of functions from xbytor’s stdlib;
    var ref = new ActionReference();
    ref.putIndex(cTID("Path"), thePath + 1);
    /*for (var l = 0; l < myDocument.pathItems.length; l++) {
        var thisPath = myDocument.pathItems[l];
        if (thisPath == thePath && thisPath.kind == PathKind.WORKPATH) {
            ref.putProperty(cTID("Path"), cTID("WrPt"));
            };
        if (thisPath == thePath && thisPath.kind != PathKind.WORKPATH && thisPath.kind != PathKind.VECTORMASK) {
            ref.putIndex(cTID("Path"), l + 1);
            };
        if (thisPath == thePath && thisPath.kind == PathKind.VECTORMASK) {
            var idPath = charIDToTypeID( "Path" );
            var idPath = charIDToTypeID( "Path" );
            var idvectorMask = stringIDToTypeID( "vectorMask" );
            ref.putEnumerated( idPath, idPath, idvectorMask );
            };
        };*/
    var desc = app.executeActionGet(ref);
    var pname = desc.getString(cTID('PthN'));
    // create new array;
    var theArray = new Array;
    var pathComponents = desc.getObjectValue(cTID("PthC")).getList(sTID('pathComponents'));
    // for subpathitems;
    for (var m = 0; m < pathComponents.count; m++) {
        var listKey = pathComponents.getObjectValue(m).getList(sTID("subpathListKey"));
        var operation1 = pathComponents.getObjectValue(m).getEnumerationValue(sTID("shapeOperation"));
        switch (operation1) {
            case 1097098272:
                var operation = 1097098272 //cTID('Add ');
                break;
            case 1398961266:
                var operation = 1398961266 //cTID('Sbtr');
                break;
            case 1231975538:
                var operation = 1231975538 //cTID('Intr');
                break;
            default:
                //		case 1102:
                var operation = sTID('xor') //ShapeOperation.SHAPEXOR;
                break;
        };
        // for subpathitem’s count;
        for (var n = 0; n < listKey.count; n++) {
            theArray.push(new Array);
            var points = listKey.getObjectValue(n).getList(sTID('points'));
            try {
                var closed = listKey.getObjectValue(n).getBoolean(sTID("closedSubpath"))
            } catch (e) {
                var closed = false
            };
            // for subpathitem’s segment’s number of points;
            for (var o = 0; o < points.count; o++) {
                var anchorObj = points.getObjectValue(o).getObjectValue(sTID("anchor"));
                var anchor = [anchorObj.getUnitDoubleValue(sTID('horizontal')), anchorObj.getUnitDoubleValue(sTID('vertical'))];
                var thisPoint = [anchor];
                try {
                    var left = points.getObjectValue(o).getObjectValue(cTID("Fwd "));
                    var leftDirection = [left.getUnitDoubleValue(sTID('horizontal')), left.getUnitDoubleValue(sTID('vertical'))];
                    thisPoint.push(leftDirection)
                } catch (e) {
                    thisPoint.push(anchor)
                };
                try {
                    var right = points.getObjectValue(o).getObjectValue(cTID("Bwd "));
                    var rightDirection = [right.getUnitDoubleValue(sTID('horizontal')), right.getUnitDoubleValue(sTID('vertical'))];
                    thisPoint.push(rightDirection)
                } catch (e) {
                    thisPoint.push(anchor)
                };
                try {
                    var smoothOr = points.getObjectValue(o).getBoolean(cTID("Smoo"));
                    thisPoint.push(smoothOr)
                } catch (e) {
                    thisPoint.push(false)
                };
                theArray[theArray.length - 1].push(thisPoint);
            };
            theArray[theArray.length - 1].push(closed);
            theArray[theArray.length - 1].push(operation);
        };
    };
    // by xbytor, thanks to him;
    function cTID(s) {
        return cTID[s] || cTID[s] = app.charIDToTypeID(s);
    };

    function sTID(s) {
        return sTID[s] || sTID[s] = app.stringIDToTypeID(s);
    };
    // reset;
    app.preferences.rulerUnits = originalRulerUnits;
    return theArray;
};
////// create a path from collectPathInfoFromDesc2012-array //////
function createPath2018(theArray, thePathsName) {
    var originalRulerUnits = app.preferences.rulerUnits;
    app.preferences.rulerUnits = Units.PIXELS;
    // thanks to xbytor;
    cTID = function (s) {
        return app.charIDToTypeID(s);
    };
    sTID = function (s) {
        return app.stringIDToTypeID(s);
    };

    var desc1 = new ActionDescriptor();
    var ref1 = new ActionReference();
    ref1.putProperty(cTID('Path'), cTID('WrPt'));
    desc1.putReference(sTID('null'), ref1);
    var list1 = new ActionList();

    for (var m = 0; m < theArray.length; m++) {
        var thisSubPath = theArray[m];

        var desc2 = new ActionDescriptor();
        desc2.putEnumerated(sTID('shapeOperation'), sTID('shapeOperation'), thisSubPath[thisSubPath.length - 1]);
        var list2 = new ActionList();
        var desc3 = new ActionDescriptor();
        desc3.putBoolean(cTID('Clsp'), thisSubPath[thisSubPath.length - 2]);
        var list3 = new ActionList();

        for (var n = 0; n < thisSubPath.length - 2; n++) {
            var thisPoint = thisSubPath[n];

            var desc4 = new ActionDescriptor();
            var desc5 = new ActionDescriptor();
            desc5.putUnitDouble(cTID('Hrzn'), cTID('#Rlt'), thisPoint[0][0]);
            desc5.putUnitDouble(cTID('Vrtc'), cTID('#Rlt'), thisPoint[0][1]);
            desc4.putObject(cTID('Anch'), cTID('Pnt '), desc5);
            var desc6 = new ActionDescriptor();
            desc6.putUnitDouble(cTID('Hrzn'), cTID('#Rlt'), thisPoint[1][0]);
            desc6.putUnitDouble(cTID('Vrtc'), cTID('#Rlt'), thisPoint[1][1]);
            desc4.putObject(cTID('Fwd '), cTID('Pnt '), desc6);
            var desc7 = new ActionDescriptor();
            desc7.putUnitDouble(cTID('Hrzn'), cTID('#Rlt'), thisPoint[2][0]);
            desc7.putUnitDouble(cTID('Vrtc'), cTID('#Rlt'), thisPoint[2][1]);
            desc4.putObject(cTID('Bwd '), cTID('Pnt '), desc7);
            desc4.putBoolean(cTID('Smoo'), thisPoint[3]);
            list3.putObject(cTID('Pthp'), desc4);

        };

        desc3.putList(cTID('Pts '), list3);
        list2.putObject(cTID('Sbpl'), desc3);
        desc2.putList(cTID('SbpL'), list2);
        list1.putObject(cTID('PaCm'), desc2);
    };

    desc1.putList(cTID('T   '), list1);
    executeAction(cTID('setd'), desc1, DialogModes.NO);

    // name work path;
    var desc30 = new ActionDescriptor();
    var ref6 = new ActionReference();
    var idPath = charIDToTypeID("Path");
    ref6.putClass(idPath);
    desc30.putReference(charIDToTypeID("null"), ref6);
    var ref7 = new ActionReference();
    ref7.putProperty(idPath, charIDToTypeID("WrPt"));
    desc30.putReference(charIDToTypeID("From"), ref7);
    desc30.putString(charIDToTypeID("Nm  "), thePathsName);
    executeAction(charIDToTypeID("Mk  "), desc30, DialogModes.NO);
    /// get index;
    var ref = new ActionReference();
    ref.putProperty(stringIDToTypeID("property"), stringIDToTypeID("itemIndex"));
    ref.putEnumerated(charIDToTypeID("Path"), charIDToTypeID("Ordn"), charIDToTypeID("Trgt"));
    var pathDesc = executeActionGet(ref);
    var myPathItem = activeDocument.pathItems[pathDesc.getInteger(stringIDToTypeID("itemIndex")) - 1];
    app.preferences.rulerUnits = originalRulerUnits;
    return myPathItem
};
////// determine selected path, updated 09.2015 //////
function selectedPath2020() {
    try {
        var ref = new ActionReference();
        ref.putProperty(stringIDToTypeID("property"), stringIDToTypeID("targetPathIndex"));
        ref.putEnumerated(charIDToTypeID("Dcmn"), charIDToTypeID("Ordn"), charIDToTypeID("Trgt"));
        var docDesc = executeActionGet(ref);
        return docDesc.getInteger(stringIDToTypeID("targetPathIndex"));
        return app.activeDocument.pathItems[docDesc.getInteger(stringIDToTypeID("targetPathIndex"))]
    } catch (e) {
        return undefined
    }
};
////// shape layer //////
function strokeLayer(theName) {
    // =======================================================
    var idnull = stringIDToTypeID("null");
    var idcontentLayer = stringIDToTypeID("contentLayer");
    var idsolidColorLayer = stringIDToTypeID("solidColorLayer");
    var idRGBColor = stringIDToTypeID("RGBColor");
    var idred = stringIDToTypeID("red");
    var idgrain = stringIDToTypeID("grain");
    var idblue = stringIDToTypeID("blue");
    var idcolor = stringIDToTypeID("color");
    var idstrokeStyle = stringIDToTypeID("strokeStyle");
    ////////////////////////////////////
    var desc11 = new ActionDescriptor();
    var ref4 = new ActionReference();
    ref4.putClass(idcontentLayer);
    desc11.putReference(idnull, ref4);
    var desc12 = new ActionDescriptor();
    var desc13 = new ActionDescriptor();
    var desc14 = new ActionDescriptor();
    desc14.putDouble(idred, 255);
    desc14.putDouble(idgrain, 255);
    desc14.putDouble(idblue, 255);
    desc13.putObject(idcolor, idRGBColor, desc14);
    ////////////////////////////////////
    var desc15 = new ActionDescriptor();
    var idstrokeStyleVersion = stringIDToTypeID("strokeStyleVersion");
    desc15.putInteger(idstrokeStyleVersion, 2);
    var idstrokeEnabled = stringIDToTypeID("strokeEnabled");
    desc15.putBoolean(idstrokeEnabled, true);
    var idfillEnabled = stringIDToTypeID("fillEnabled");
    desc15.putBoolean(idfillEnabled, false);
    var idstrokeStyleLineWidth = stringIDToTypeID("strokeStyleLineWidth");
    var idpixelsUnit = stringIDToTypeID("pixelsUnit");
    desc15.putUnitDouble(idstrokeStyleLineWidth, idpixelsUnit, 3.000000);
    var idstrokeStyleLineDashOffset = stringIDToTypeID("strokeStyleLineDashOffset");
    var idpointsUnit = stringIDToTypeID("pointsUnit");
    desc15.putUnitDouble(idstrokeStyleLineDashOffset, idpointsUnit, 0.000000);
    var idstrokeStyleMiterLimit = stringIDToTypeID("strokeStyleMiterLimit");
    desc15.putDouble(idstrokeStyleMiterLimit, 100.000000);
    var idstrokeStyleLineCapType = stringIDToTypeID("strokeStyleLineCapType");
    var idstrokeStyleRoundCap = stringIDToTypeID("strokeStyleRoundCap");
    desc15.putEnumerated(idstrokeStyleLineCapType, idstrokeStyleLineCapType, idstrokeStyleRoundCap);
    var idstrokeStyleLineJoinType = stringIDToTypeID("strokeStyleLineJoinType");
    var idstrokeStyleMiterJoin = stringIDToTypeID("strokeStyleMiterJoin");
    desc15.putEnumerated(idstrokeStyleLineJoinType, idstrokeStyleLineJoinType, idstrokeStyleMiterJoin);
    var idstrokeStyleLineAlignment = stringIDToTypeID("strokeStyleLineAlignment");
    var idstrokeStyleAlignCenter = stringIDToTypeID("strokeStyleAlignCenter");
    desc15.putEnumerated(idstrokeStyleLineAlignment, idstrokeStyleLineAlignment, idstrokeStyleAlignCenter);
    var idstrokeStyleScaleLock = stringIDToTypeID("strokeStyleScaleLock");
    desc15.putBoolean(idstrokeStyleScaleLock, false);
    var idstrokeStyleStrokeAdjust = stringIDToTypeID("strokeStyleStrokeAdjust");
    desc15.putBoolean(idstrokeStyleStrokeAdjust, false);
    var idstrokeStyleLineDashSet = stringIDToTypeID("strokeStyleLineDashSet");
    var list1 = new ActionList();
    desc15.putList(idstrokeStyleLineDashSet, list1);
    var idstrokeStyleBlendMode = stringIDToTypeID("strokeStyleBlendMode");
    var idblendMode = stringIDToTypeID("blendMode");
    var idnormal = stringIDToTypeID("normal");
    desc15.putEnumerated(idstrokeStyleBlendMode, idblendMode, idnormal);
    var idstrokeStyleOpacity = stringIDToTypeID("strokeStyleOpacity");
    var idpercentUnit = stringIDToTypeID("percentUnit");
    desc15.putUnitDouble(idstrokeStyleOpacity, idpercentUnit, 100.000000);
    var idstrokeStyleContent = stringIDToTypeID("strokeStyleContent");
    var desc16 = new ActionDescriptor();
    var desc17 = new ActionDescriptor();
    desc17.putDouble(idred, 0.000000);
    desc17.putDouble(idgrain, 0.000000);
    desc17.putDouble(idblue, 0.000000);
    desc16.putObject(idcolor, idRGBColor, desc17);
    desc15.putObject(idstrokeStyleContent, idsolidColorLayer, desc16);
    var idstrokeStyleResolution = stringIDToTypeID("strokeStyleResolution");
    desc15.putDouble(idstrokeStyleResolution, 72.000000);
    desc12.putObject(idstrokeStyle, idstrokeStyle, desc15);
    ////////////////////////////////////
    desc12.putString(stringIDToTypeID("name"), theName);
    desc12.putObject(stringIDToTypeID("type"), idsolidColorLayer, desc13);
    desc11.putObject(stringIDToTypeID("using"), idcontentLayer, desc12);
    executeAction(stringIDToTypeID("make"), desc11, DialogModes.NO);
};