I agree with the suggestion on the substrate change, I personally like using cypress mulch. It holds humidity pretty well and is more resistant to mold. And a full biodrain system isn't necessary, I was just suggesting throwing in a potted plant.

If you were contemplating doing away with the UV light, maybe consider a setup with a under tank heater with a thermostat (Herpstats are the best but pricey IMO, but you can get the Jumsptart thermostat on Amazon for like $30 to start with) and switching to a CHE bulb on a dimmer? Will be easier to keep track of temps when you aren't home. 100w seems pretty powerful for an enclosure of that height