What is his current humidity, keep misting every few hours, you could try adding some wood surfaces for him to scrape along, you could also try adding a hide box with some moss substrate, and if you're having bad sheds then replace he substrate with something that holds humidity better (orchid bark, cypress mulch etc)
Get a warm damp towel let him slither through it apply gentle pressure.. If this helps then continue to do it.. If it doesn't then just leave him in there and try out the suggestions listed.
I also use a wooden viv and a ceramic heater and was having humidity problems, so I bought some orchid bark and now the humidity is fine! I will also be buying a Perspex glass sheet for the bottom of the tank to stop wood rot.
How are you measuring temps with a digital thermometer? Consider buying a temp gun also, then you can compare the temps between the thermometer and the temp gun. If he is never using the warm hide it could be hotter than your thermometer is telling you, where do you have the thermometer probe placed?
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