Hey, I used to do this by making an action that would place a single ai file which contains a spot-color cut contour swatch. When I pressed the button, it would automatically place the rectangle into my active document from the filesystem and immediately delete the swatch. Now the spot color is in the active document!
But to help you with your script, we really need to see what the code is. It could be anything and everything.
After watching your video the problem is clear: your add cutcontour swatch is created by a script, which is played by an action. But you are also trying to run that action by a script in the 2nd round when it doesn't work. That is because, well, it doesn't work like that. You can only play an action from a script that has no scripts, or you can play an action that has a script, but only from inside Illustrator.
For your swatch needs though, you really don't need a programmer because you can use my technique and simply place & delete a rectangle. When you do need a programmer, keep in mind the action-script interoperability so that you guys don't write a huge library around your current perception and it doesn't work.