Hi clairebear2k6 It's hard to answer your question. If he truly wants to leave and is determined to leave then I'd answer with a yes, it's better to let him go.
I read your other posts and it sounds like a really tough situation for you.
I think you might get more response and support by posting this question in another forum where more people may see it. I only noticed it because I was searching for unanswered threads.
I just looked and I can't find a"general" support forum but maybe the coping/emotions forum might get more responses.
Or maybe you might find one you think is good. I don't see a post by you in the new members forum. Welcome to PC and I hope you can also find support here for a parent's struggles raising a special needs child as well as as insights and support for the child.
I wish you well.