Your snake is most definitely getting ready to shed! He's probably on the warm side because of that, as well as the fact that some corns prefer to be warm all the time. Differing hide sizes usually aren't a problem, but you might make the cool side hide the same as the warm side to see if he uses it more.

Re: drinking, I have some snakes that I've had for 3 years and have never witnessed them drinking. I'm pretty sure they are doing so.

With regards to morph... can we see a picture of his belly? Does he have checkers, or is his belly patternless (or maybe with some red speckling)? His side pattern looks diffused to me.