If the boyfriend was going to stand up to his father he would have done it already. The same for "encouraging other family members to intervene". They won't do it, and they will turn against the LW because they have to blame someone.
Three choices:
1. Listen to this vile human being until the day he departs the planet. Do you want a relationship where you look forward to the death of a relative? 
2. Try to convince your BF to turn his back on his family. (Hint: he won't.)
3. Move on to another man; this one and his family are not for you. 
Don't wait for the moment when you hear your children spouting grandpa's opinions, and realize that you could/ should have escaped.