Using Adjustment Layers in 3D space

The bulge effect should not be on an adjustment layer.

To solve the parallax problem add Bulge to Map layer. Then you need to write some expressions that look at the straight line between the center of the magnifying glass and the camera then project that position onto the map layer. You will also need to calculate the distortion when there is an angle between the magnifying glass and the camera. That's more vector math than I can do in my head, but it is doable.  You are going to need some layer and comp space transformations in the expression if there is any parenting involved.

Here's an illustration of the problems involved when the Magnifying glass is above the Map and you need to animate the displacement.

I set up a Point light with zero shadow diffusion and Shift + parented it to the camera so the projection would line up. I set the Magnifying glass layer (red circle) to cast a shadow and have 100% light transmission so the shadow would fall accurately on the Map layer (the grid). 

If this was my project I would set up Freeform Pro and use the same projection technique to distort under the magnifying glass. Here is a tutorial on how to do that. Too bad you can't do that with the Magnify Effect.

You'll need to do an expression 'layer space transform' here. Does that terminology mean anything to you?

Off the top of my head... try this expression on your magnify effect position:

layer = thisComp.layer("Null 1")
layer.toComp([0,0,0])

Adjustment layrs break 3D rendering, so I'm not even sure what the point of the exercise would be. You'd have to do it in 2D on top of the pre-composed 3D stuff no matter what. The rest is simply to vague to make any sense of it. It may of course be possible to facilitate the process by e.g. creating some extra 3D Nulls and reference them in an expression, but without knowing your exact setup this isn't going anywhere, either. Simply be more specific and provide at least soem screenshots.

Mylenium