Remember as frustrating for you as this is, it's worse on your snake living through the tweaking of it's home. Personally if you are fighting this humidity issue so much I'd pull that moss, put down only some layers of plain white paper towel or newspaper as substrate, get a small water dish with little surface area (just grab something at the dollar store like a white ceramic ramekin for instance) and see how the tub settles out then. With this high humidity are you getting condensation anywhere on the tub lid?