ditch the lamp as previously said, I have a 30 gallon tank that i keep mine in and the substrate temps in my snakes hides are perfect using a thermostat. The ambient temp is lower but that isnt as important as far as i know. My snake is healthy and humidity is at 50-60%.

That lamp is your problem, also like previoiusly said try covering your screen with something, I use a towel, keeps heat and humidity in.