As for the anger itself, Im not really going to be much of a help there. I usually just go for a drive with the radio blaring, but Im sure thats not the best option when Im feeling that way. However I had a similar situation with my inlaws within the past few years. The worst part of the whole thing was DH didnt defend me at first! That caused a LOT of problems between us. Finally he realized it and came around. I think the first thing you have to do is if you are in fact I the right(which I believe you are) get your DH to see that and fully support you. Family or not, you are his DW and YOU should come first. That makes a huge difference. In the end I didnt speak to my inlaws(MIL, BIL and his DW) for about a year. MIL finally realized she was worng and made a peace offering. We then started talking again. As for BIL and his family I didnt speak to them until I just saw them at MILs wake, and Im sure we wont be seeing them anymore.
I guess I go with the "elimate the source of stress" theory, whether its the right thing to do or not.
Good luck! I hope this all works out for you.