H.H.
Reading this bought a tear to my eye. My heart is broken for him- I can't image how you feel. My son is a bit of a loner, but it is by his choice- he likes to be alone. He used to have a really hard time finding something to talk about with other boys. He doesn't watch a lot of TV or play a lot of video games with seemed the other kids did- so he was always left out. He never knew what they were talking about. He found one boy in his class this year that also loves dragons so they spend most of the time drawing dragons and pretending to slay them on the playground. But his true passion is bugs..he has yet to find a "bug buddy".
You should definitely get him into a group activity- sports or other-if he is part of something that they all relate to, it might make it easier for him to fit in.
It would be good for you to see how he relates to other children so you can see why he is having trouble.