I agree that it is worth re-intoducing them slowly and trying again.

http://www.piftails.com/main/article...ingnewcat.html

But if you can't keep him, what about a non-kill shelter or finding him a home yourself.

TNR is fine for the wild kitties but wouldn't it be wonderful if he could have a home.

BTW my vet says it takes 6 months are neutering for all male hormones to work out of his system.

Good Luck whatever you decide.