I can see why you kept silent when you were insulted out of respect for your BF and his connection to this family.
In this case, the BF should have spoken up himself to remind this family that such comments towards you are not welcome and would not be tolerated, when you were called high maintenance and jokes were made about your eating habits. He should have done so out of respect for you, because he clearly knew you were not comfortable. You have at best a tenuous connection with this family while his is quite deep. As such it is his place to confront them about their apparent rudeness, not yours. After all, if not for him, I am sure you would have nothing to do with these people. He knew this as well, because he thanked you for coming with him. Since he knew all these things and did not act, I would begin to wonder about his character if I were you.
Their loss, while regrettable and sad, is no excuse to insult you. Everybody has problems, and most of us have experienced loss as well. I have to commend you for remaining calm while under attack, that must have been very difficult. I agree that disentangling yourself from these people sounds like a good idea.