Ok Ok Ok.

Thermostat probe goes OUTSIDE the tank. Always. Do not put it inside the tank.

Get a thermoMETER probe and put that in the tank with the snake. Put it under the substrate in the middle of the UTH. You need to measure the hottest point your snake can reach (no higher than 94*). They can get under the substrate (move it around) if they want to and they will.

If your ambient temps are not high enough, either get another UTH with a dimmer and hook that up to the extra socket in the reptitemp. You will also need another thermometer probe. You can use the heat lamp if you want, but as you said, they suck humidity. Another option would be a space heater for the room.

If humidity is really getting to be an issue, switch to tubs. You will never have another problem with humidity.