If you can bump his humidity up, that's huge for getting good clean sheds. At this point I would give him a soak for a couple hours in a small tub. Use luke warm water, try to match his temp so you don't shock him, about an inch deep. Make sure the tub breaths with cap on, you could just poke a couple holes to be safe. Put the tub with him in it obviously, into his enclosure to keep the temp right. After a couple hours you can release him back into his enclosure and he should be able to get it off.