So if you have too much humidity while being able to reach proper temps with the towel setup, then you should be thinking about switching to a different substrate that carries little to low humidity. If your humidity actually stays at about 70% year round I’d be thinking about aspen or paper as you have no need for extra humidity generated by the substrate.
Yes, ambient air temperature is important however and no a uth on the cold side (from my experience) doesn’t raise ambient air temperature very much, at least not to the extent of a lamp or CHE.
A lot of these answers your seeking are found only with troubleshooting and trial and error on your part. It can be very frustrating to nail it down, but once you do, you can check off one of the most difficult things about snake ownership. There is nothing wrong with tanks BUT by design they are not intended for reptiles so you have to be a bit more creative and experimental.
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