To help with humidity cover up the top some, plexiglass or even foil does the trick. It will also help with ambient temp.

OP you mention using an incandescent bulb form walmart on the cool side. Your snake won't like that very much. They are nocturnal so bright white light is not the best thing to use. At the very least make sure its off at night. The infrared bulb is fine to leave on all night though. Some folks on here say blue is better though.