Place the foil tape on most of the screen but leave a window where the heat from the lamp can pass through.

As for the humidity issue I add moss to the hides. I leave it in there at all time. I keep it damp during a shed and during regular time I will damped it and allow it to dry out before dampening again.

I have a bp in a 40gal glass tank using cypress, uth, and a 100watt che with a 60watt lamp over it. Adding the humid hides gives me perfect sheds with little effort on my part.

I do have a mister on the tank but that is more for the live plants. So adding humid hides and misting daily should give you good sheds without changing your substrate but adding cypress would only help.

Your water bowl is a shape that could easily be tipped by your snake. This could flood your tank and could cause some problems. Many people find nice cheap bowls at dollar stores. I personally use ceramic dog bowls in many of my cages. They work great.