M.,
I don't know what I could possibly say to make it easier for you to handle this sticky situation. And most of the time when we (women) are venting we really jsut want somebody to listen anyway :-).
you're not alone, I am in a similar situation, although different, and tailored to my own crazy whacky in-laws. Mine is my SIL - she's such a whack job and nothing I will ever do will please her. Did I mention she's incredibly pretentious? She was talking to my husband about our basement, putting carpet in, she asked wht the square footage was and when he told her she said 'that's not possible! your basement is bigger than mine?!?!) My husband is much closer with his family than I am (my brother still has not seen my soon-to-be 16 month old son, and havent heard from him about my new 2 month old daughter - but it really doesn't bother me). She moved darn near wisconsin... it's almost a 2 hour drive for us - she hasn't been out here since 2004, but complains we never come out to visit her two boys, and what a joke of an uncle my husband is. This caused quite a stir in the family because I can't keep my mouth shut - you insult my husband I'm going to defend him. Anyway, I've learned to cope with her, but my MIL still has her share of digs - though very passive aggressive, and in such a way that my husband cannot see it (she came by one day and I was looking through my recipe book, she gave a little laugh and said 'oh, what? are you gonna COOK?' - like she believes that I am not capable of comparing to her superior culinary skills and her precious baby boy is getting sub-par meals - WHATEVER!)
Now i just distance myself somewhat, and as much as I hate it, I bite my tongue at family functions and put on the fake facade, just like them. I don't recommend trying this if you've had a couple drinks, i know for me, the liquor loosens my tongue way too much!
I remind my husband that he doesn't have to deal with in-laws. I saw my father last in December - for my sons first birthday - didn't even see him on christmas, he sent envelopes with my sister, and a tickle me elmo that is still in the garage getting the cigarette smell off it. my husband and i jokingly call it 'smoke me out elmo'. And since my mother passed away before we were married, he doesn't have a MIL :)
UGH! sometimes I am so thankful my family isn't up my a$$ like his - but unfortunately I still have to deal with them - UGH!!!
So I'm sorry I couldn't give any practical advice, but at least I can empathize - you're not alone!!! :)
hang in there...