That's very helpful, thanks!!

I will definitely switch to the substrate you suggested.
I added a small shallow water dish and sprinkled a little water in his hide box (which has a folded paper towel in it that I change when needed) and he's already doing a lot better. His skin seems much more hydrated, he's even moving around more than he was before! He sure is a lively one, here's a picture of him (he's named Link, by the way):::