Do not remove the snakes only heat source!! You need to guard the snake from the bulb. A cage or surround that prevents the snake from contacting the light. A uth can also work but don't remove the bulb until you have some other source figured out! There is no single solution every persons set up is different, tanks have been used successfully for many many years so there is no need to go buy something else.

Humidity can be a bit of a challenge but heat is critical humidity is a secondary concern. The bulb can be made to work but it must be separated from the snake. You mentioned that the rheostat worked with the bulb you can use it to drop the power back but you will still need a cage, or to replace it with something else. If you have only the single animal and I am guessing that you have it in a regular room that have variable room temps you might look at a T-stat to control it over the rheostat. I like proportional controls like a herpstat but they cost more than some of the alternatives. If you continue to use a glass tank you can manage with something like a hydrofarm johnson or ranco. They don't do well with thin materials and direct heat like a uth attached directly to a plastic tub. The on/off spikes can be dramatic with out a bit of a buffer to take the 'edge off'