feeling great expressed thing beautifully. what you are doing is the best thing. Just because he is older in age doesn't mean that you don't care, you are even more concerned because he hasn't flourished into an adult like your daughters.
Kids are supposed to leave the next and be on their own, as parents we want them to have better and to succeed. when all is said and done, he may be OK with help and meds and this story COULD have a happy ending, where he thanks you for the swift kick in the buttisimo.
you can be realistic and optomistic too. I hope he likes the therapy group....it will be his only entertainment without internet and tv reruns.