Yes, you can spritz some water onto the aspen. It won't hurt anything. Just don't get it soaking wet. But if your humidity is staying that high and constant, you probably don't have to do anything at all.

What kind of hides are you using? Are they small and tight-fitting for him? Or the open-sided half-logs? If you're using the logs, try replacing them with small plastic bowls or saucers that you can cut an entrance into. If they're already small and snug...then you just have to wait for the snake to find them and feel certain (in its own little primitive brain) that no other critters have or will claim those perfect little caves. You don't have to MAKE him do anything.

As for eating...if it's feeding day, try to feed him. Do you know what he was eating before you brought him home? Best to stick with that, whatever it was...and then, once you're certain he's comfortable enough to eat with you, you can start the process of trying to switch methods if you prefer. If you don't know what he was eating and can't find out....then try what you wish and see if he'll eat it. It may take a few weeks to find the right meal for him....but be patient and don't try to feed too often. Once a week is plenty, even if he's refusing. Offering food more often than that can cause more problems than it is likely to solve.