Is his tank near a high traffic area in your house? Lots of tv noise, dogs barking, or just people keep walking by his tank during the day? You did not disclose that detail in your list. And UTH from 80-87 is weird to me... A bp needs no less than 85 if I recall correctly. Some snakes like to dig. I use aspen for mine even though he does not use it, my other python (not a bp) does though.

Did you try the 6 qt method from Deb? I did that and my bp started to eat.