How are you measuring the temperature of the UTH? There is a difference between a dimmer and a thermostat, which do you have? A thermostat is much better than a dimmer, especially if your house temp fluctuates.

As long as your house stays in the 70's, you shouldn't need any supplemental heating on a tub. They hold temps and humidity much better than tanks.

Honestly, I would loose the reptile carpet. After he pees or poos on it, it is basically toast. That stuff is hard to clean and even after you have cleaned it, it can still have an awful smell to it which means bacteria is growing.