He's eating! Finally!!!
After moving the water bowl closer to the UTH, installing the screen window I posted above, and covering half the top with aluminum foil, I finally got the humidity up to a low of 55% and a high of 70% after misting. Right now, it's at 62% and I misted the viv well over an hour ago.
He's just getting done swallowing the little hopper. It had been a couple of weeks since he'd eaten. I'll offer another mouse in several days.