You may have missed the major clouding in his eyes since they like to hide when they're in blue, as you've experienced. Also, I've never found any consistency in how clouded my adult male's eyes become. All sounds fine regarding the impending shed.

Not so sure about the humidity spike, it's pretty amazing what can affect the humidity levels inside the vivarium, but leaving a dry towel on the top shouldn't do anything. That is, unless, you have a wooden vivarium with vents at the back, and it covered a vent somewhere at the back? Although you say it was folded up. Hrm..