The hiding under the water bowl is nothing to worry about. Snakes love tight, secure fitting hides and beneath the water bowl provides just that.
Now for a little confusion...are you're sure you're feeding rats and not mice? Mice come in fuzzies and hoppers while rats come in fuzzy, pups and weaned.
HUGE difference. If you're feeding fuzzy mice and waiting on hopper mice they are WAY too small.
Lastly, it's extremely important to distinguish between poop and regurge. If it's poop it's nothing to worry about. If it's regurge you need to determine why it happened.
You'll also need to give the snake AT LEAST 2 weeks to recover since regurgitating can beat up their insides.