You sound like a lovely mum, actually a lovely couple. I always stress about my kids getting shunned by grandparents etc As much as it destroys me that my mother shuns Me, people always tell me that, as much as I worry for my kids, of course it doesn't affect them so much because they are a generation apart, and we are their buffet from "the outrageous fortune of life's slings and arrows ( and shunners)" - as you are your sons.
What I'm saying is although it's a difficult journey for him, no doubt about that, you cannot do more than you are in helping him steer a course. Even worrying about others like him! On a practical side note getting him involved in helping others makes outside connections/friendships and takes the focus off his own worries! Maybe something like volunteering for a cult hotline or similar that takes his own negative experience and moulds it into something positive( may help with the finding an empathetic mate bit too!).