I can soooooo sympathise with you, I just wanna reach out and give you a big hug .
I've had problems with my MIL ever since I came into DH's life. Before we were married we broke up once, and his mother was a huge part of that. I am sort of lucky in a sense that he agrees with me that his mother is completely out of line and just not a nice person. At first I tried to be nice and tried to fit in, as you do with your other halves family. Then at one point I said to myself "Why am I putting up with this? They are no better than me. I do not deserve to be treated this way". DH agreed and we majorly cut them out of our lives. And just so you know, that is your right to do so. It is up to you how much you want to have to do with them. you do NOT have to put up with being treated that way and you did the RIGHT thing speaking up for yourself, I just want you to know that. Anyways, after the in laws got the hint that they wouldn't be seeing us anymore if they treated us like that, they got a bit better. it took time - years - but now MIL is definitely better. she hasn't totally improved, there are times when she tries it on but we just back off and she gets the hint again.
Can I just ask, how much damage can they really do if they live interstate? They can't be knocking on your door and hanging around criticising everything you do. I'm not in your situation but is there any way you could just ignore them and their ridiculous attitude? Just focus on you and your family, that is what is most important. There are always going to be people in life that don't agree with what you do, that's just life. It shouldn't stop you from doing what you believe in