Ok first of all calm down and breathe. I read a lot of stress in your post and rightly so, but if you are stressed, you will make him worse. He could just be in shock, but he needs to eat. At this point, try nuking his canned food, put a little bit on his paw so he has to lick it off. Get down to his level and just sit with him, put cat treats around you and see if he comes out, dim the lights in his room, play classical music really low for him. Buy a bottle of feliway spray and spray it liberally in the room he is at.
How long has he NOT been eating? Try things that strays find in dumpsters, boiled chicken, put it right on the floor, try raw pieces of meat, at this time, just something for him and see if he goes for it? Sardines, tuna? Mackeral? shredded cheese? Cottage cheese? Boiled hamburger and rice- is he NOT eating anything? Did you know he was ill when you adopted him? Has blood work been run? Is he drinking? These are all important questions, cats can go only a few days without eating before they get fatty liver disease. You need to get him to eat, whatever it takes. If you have catnip, put a little on his food plate, feed on a plate or saucer not a bowl-