Well, this is a very noble and generous gesture of yours! Thank you on behalf of the poor bird! It's also a huge and long-termed commitment that will imply a lot of work with very little to show for a long time. Wild-caught birds are mean, mean, mean and noisy, noisy, noisy. They simply don't like humans and who can blame them? And they are noisy because they learned to vocalize in the wild, in the middle of a large flock. Nothing like hand-fed birds, I assure you. I hope you have a birdroom where he can be cage-free because wild-caughts don't do well in cages, not even for a couple of hours, and toos are very, very destructive animals (they will chew not only furniture but walls and floors, too

). I would start by making an appointment with your avian vet for a complete physical because, obviously, birds are not meant to live in a basement and he has to be, at least, 17 years old, if not older. just letting him be himself and setting yourself up as the provider of food. Once he gets a clean bill of health, start by gaining his trust and then start thinking about taming him. No use even trying now, it won't do you any good, it takes a long, long time to gain the trust of a wild caught that has been neglected and/or abused as this bird has been and that is the first step toward any kind of a relationship with him. Get him used to your presence to the point that he doesn't try to put distance between you and him and, when this happens, start offering him treats from your hand. Once he starts taking them, start training him to step on a stick and take if from there.
A word of caution, go into this with your eyes wide open. You might be able to have some kind of a relationship with him but it will never be anything that resembles the kind that people have with hand-fed birds so don't expect a miracle. But what you are doing is great and you might well be saving this poor animal's life so kudos to you!