I know you said that the sides are covered with some sort of transparent paper but it seems like you have a very scares BP so you want to make him feel as secure as possible.
Personally, I'd suggest moving him out of that large enclosure into a 20 gallon but don't know if that's available to you. A smaller enclosure should make him feel more secure and will also help you with heating issues.
Considering that the terrarium is on the floor, you have to really monitor the temps to make sure that they're not falling down even more during the night. Like someone already mentioned, your temps are very low. I'd suggest keeping the cool side at minimum of 80. You may also want to cover the top of the enclosure that doesn't have the CHEs with acrylic plexi glass. This should help with heat and humidity loss.
I'd also cover the back and sides with black or dark construction paper or something along that line to provide him additional security.
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