I've been in cat rescue for a number of years and I can tell you there is every chance that Itty Bitty could come indoors and decide to live there happily. I've been in cat rescue for about 13 years and most everyone I know has experienced this. I trapped a feral cat's three kittens. The two boys were absolutely crazed from the get-go. They were TNR; however, their sister only wanted to be held and warm and fed and never to see outdoors again. I trapped three more siblings a few years ago. The two females were wild Indians; however, their brother thought he'd discovered paradise indoors and never wanted to leave. So there is a huge possibility that you can continue working with Itty Bitty and he can become an indoor only cat and live happily ever after. There's no rhyme nor reason as to why a cat born outside wants to be inside and others don't. I'd say because you've gotten as far as you have with him that he's a great candidate for indoor living. Good luck with him!