WOW, one more thing I would like to relay to you. Although you don’t feel that what your son is doing is “normal”, because it is not normal for you and what you know. It is quite normal for what he is going through and for what most children in his situation goes through even down to the cereal for meals. He isolates himself from the family, not because he doesn’t like the family or he doesn’t enjoy doing things with the family. He doesn’t WANT to like it or enjoy it. He is working on convincing himself that he doesn’t and that he doesn’t want to be a part of it.
If you ignore him, you are only helping him to isolate himself and get the job done. If you create opportunities or tempt him with ways to stay involved you may be able to get his guard down and make a connection. So when you ask him if he wants to go out for ice cream find a way to get him to go. “I’m going to go for some ice cream, I could really use some company, I would really appreciate it if you would join me” even if you have to offer to take along a friend. “would you like to bring a friend along?” or if he declines say “well maybe next time, would you like me to bring something back for you?”