This is very difficult.

You should stop all associating with them.

they put you down and he cannot stop them from putting you down, so you should stop associating with them, cold turkey and no compromises.

And then either your boyfriend grows up, or he does not, but you cannot force him to grow up.

If he wants to see you, he will have to come over or go out with you - no meetings on "their turf". If he cannot go out with you because his parents do not allow him, you just need a different boyfriend who would be more independent and mature (does not have to be older, but just more of a self made man).

Very sorry to hear that!