I would recommend much smaller hides. Those just dwarf him. If you eat frozen meals, the Smart Ones lasagna pans work well for baby hides They are a bit taller than normal and aren't sectioned off.

Try the smaller hides, possibly put a dark pillowcase over his tub, and try again in a week.

He may need to be in a smaller tub, such as a 6qt or 15qt. I've easily fit 2 hides and a water bowl in the 15qt size tub. Even have an 850g Hypo male in one and he's quite happy. He'll be getting a 27qt soon though.

Definitely get the temperatures up though. Try between 92-94 on the warm side and 82-84 on the cool side. I don't like mine to dip into the 78s if I can help it.