This is going to sound weird, but can I ask you where you live ?
That snake looks an awful lot like a male I sold last year, the markings are really, really similar.
Poor thing. I to had to rescue a snake left behind when someone moved. Except mine was in the middle of winter, and they left her to freeze to death.
Read up on our caresheets, they are the best out there in my opinion. Tweak his enclosure if needed. Give him time to shed, then about a week of peace and quiet after he sheds and see if he'll eat for you. He's not really skinny, so that is a huge bonus, and he'll be fine for a while before feeding. Oh, and just so you know hon, keeping humidity up in that tank is going to be a real PITA. I tried that for a while, then I got smart and went to tubs.
Are you prepared to feed live, if that is what he wants ? Some people do fine with live, but a lot of people can't.
I have no doubt in a month's time, you'd never know he was abandoned.
Gale