Welcome to the forum and congrats on your new baby! I was exactly the same when I got my first; constantly checking the internet to make sure he wasn't about to implode or spontaneously combust.

I would ditch the heat lamp and just have the UTH on the warm end, with the water dish on the unheated side (just preference). It sounds like you are carefully monitoring your temps though, so your setup may be just fine. I prefer aspen for snakes, as repti-bark is harder to keep clean. Humidity should be fine at 55% as long as you provide a damp hide (especially during shed time), but there's nothing wrong with going to the extra work to have it at 60%. Water dishes can be too big, and baby snakes can drown in them. However, yours sounds like a good size.

His behavior sounds great. He sounds well adjusted and low stress right now, which is very good. The "s" shape isn't always a sign of stress or aggression. Babies like to hang out in weird positions (especially spiders). As long as he isn't constantly hissing/striking at the glass he's probably just chilling out and enjoying his new home. Ball pythons don't move much unless they're exploring or looking for something to eat.

Because he sounds like he's adjusting really well, I personally would probably offer him a meal on his regular feeding day. If he doesn't take it, no big deal, but at least he'll have the chance to eat, and if he does it will be less stress for you.

Ball python yawns are adorable, so try to enjoy them as long as there aren't any worrying symptoms like breathing sounds, breathing with the mouth open, or discharge around the mouth or nose. I hope you and your baby get off to a wonderful start together!