lephi aniyus daati
1. They are not his ‘friends’ and that is not lashon hara!
2. He is angry and you are upset, that does not sound like a situation which is going to progress very far emotionally. The religious aspect of this situation is taphel to the emotional aspect. Therefore it is more important to address the emotional aspect of the situation currently. The missing ingredient is simchah.
3. It does not sound like you can directly affect your son’s feelings currently.
4. Your son has been turned off by religion so religion is not the answer to turning him back on again. Neither is benevolent parenting (making him his favourite foods etc.) a complete answer becuase this still maintains the parental aspect. You need to find something which you can do just for fun and that has no religious connotation at all and not involve your son directly in but which can be a subject for discussion.
5. Your son’s future lies not in his connection to Yiddishkeit directly but in his connection to Yiddishkeit through you. If you create a channel for this connection the other problems will resolve themselves.
Feel free to ignore all the above 🙂