I'm going to give you a list of things I freaked out about during my first month, and what I've learned since...
1. Sometimes, these guys just aren't going to want to eat for you. But it's pretty common and missing a feeding or two is not the end of the world and it won't hurt them.
2. That little brown spot on its belly is probably just that: a little brown spot, or a tiny piece of substrate sticking on your snake. It is most likely not scale rot or a snake belly invader from space hellbent on torturing you. Keep the enclosure clean and tidy and you won't have to worry about scale rot, and it sounds like you've already done your research there, so kudos.
3. They like to hide. A lot. This is good and normal. You will rarely see them roaming around, and if they are, feeding day is probably around the corner. If it's not, just double check your temps and humidity to make sure all is well.
4. For being so shy and timid, these guys are insanely curious. It's taken me about 15 minutes to type this out because my little python has tried to crawl down my bra three times, into my hair twice, and onto my laptop many more times.
5. If it jerks its head away fast, it was most likely just startled and wasn't actually trying to bite. My ball python has never actually bitten me, and only struck at me once when he got substrate stuck in his mouth and I wrestled it out (couldn't blame him there). Even then, it was the laziest, half-hearted strike I've ever seen out of a snake.