First off, he looks awesome! Enchi and OG compliment each other VERY well.
Each BP has their own personality. I have some that flinch for a second and then chill when I take them out. I have some that could care less when I reach in and mess with them. I have some that tend to ball up when they're out and then relax, and I have some that are constantly on the move. They do tend to mellow out as they get older, but that's not always the case.
For your temps, make sure that you're measuring the tub itself above where the Flexwatt is - NOT on the paper towels. That's where you want the 90ish range. When he decides he wants to move the towels around and redecorate for himself, you want to be sure that he's not going to find temps that are too hot for his liking and end up putting him in danger. Honestly, that could be the reason he's favoring the cool side (temps being too warm for his liking on the hot side). Once you have the temp directly on the tub in the right range, then you can chalk it up to him deciding what's best for himself.