The main issue with that setup is the substrate. Pacman frogs like to burrow, so a coco-fiber substrate is necessary for them to be comfortable. Also, reptile bark and moss are bad ideas as these frogs will often eat pieces of them along with their food, which can cause impaction. The coco-fiber substrate is also good for this as it won't cause impaction if it is ingested.
That might also help out your humidity issues; a moist substrate like that holds in the humidity and will keep your frog more moist than something like reptile bark. It's what I use and mine stays fine with several daily mistings from a squirt bottle.
Also, he probably isn't estivating that quickly; You'd notice a difference in appearance (do a google image search for it). He's probably just stressed from the move to another enclosure