I can identify with a few things in your post, but from sort of from your boyfriends shoes...
I was in a "relationship" with the same guy from the age of 15 to 19. My entire family loved him, my dad treated him like a son, and my dad even told him that he hopes we get married... Well, the last few months of our relationship was pretty much useless, we just drifted, didn't have the same feelings for each other so much, and I ended up cheating on him with my now husband. I've now been with my husband for just over 4 years, and even still, some of my family members don't like to be around him. My dad has never and probably will never accept him fully. My husband and my ex are two completely different types of people, which is why I guess my family was shocked and confused and angry why I chose "the lesser" of the two (as they see it). Amazingly, and I don't know how my husband does it, he just lets it roll off his back. He knows not all of my family like him, but the way he sees it, is it's their problem. He married me, not my family, and it's what happens between us that matters.
you have to keep in mind also, that your boyfriend possibly takes alot of heat about you. I also don't like attending big family get togethers for the same reason you don't; it's awkward and knowing your getting looks of death doesn't exactly make you feel welcome. It hurts and bothers me, but at the same time, I realize they'res not a whole lot I can do about it. If they don't want to accept you, fine. You don't have to be their best friends. While we all WANT to be able to get along with our in-laws, it doesn't always happen that way. My MIL LOVED me at the beginning, said I was the best thing to ever happen to her son... after a few years, she's changed her mind and I am not her favourite person. But I suck it up, and be civil when we're around each other. My husband does the same thing when he's around my family. He shows them that he's the bigger person by making small talk and showing that their opinions aren't going to affect OUR relationship together.
Don't let families tear you apart. Ask yourslef, is it so bad that it would be worth ending the relationship over? My guess is probably not. Sounds to me like his family are being childish; the same way a bully keeps picking on the same kid... if you show that it doesn't bother you, they will only get bored and stop. If they don't well then that is their own damn problem. Live your life with your man, focus on each other, and everything will work itself out
good luck!