I wouldn't worry about the house, chicken mite aren't interested in non bird hosts. clean your coop out completely, burn or throw away the bedding, treat the coop and the birds, get all new bedding and litter
Leave him there. to bring him back would be cruelty. He will adapt and it's best that he do it while he's still young.
He's seperate there and they'll get used to each other while he's growing.
He has no idea what those other things are, in a new environment and he's scared out of his mind.
He's needs a very slow introduction, it will take some time but he'll catch on.