It sounds like moving is what will be best for your family. It sounds like you need to have that talk with your husband *gently* and tell him that you feel like he's attacking you when he sides with his sister and that you would really appreciate and feel great about him taking a more supportive stance of you during his *parenting* discussions with his sister. (Does she even have kids?) It could be that as you seem new-er to the whold SAHM thing they are just trying to be helpful and offer you advice and maybe they think they are making your job easier... My mom in law was "making comments" that I found very offensive - telling my husband that I didn't take good enough care of my house, etc. He bought into it almost every time and took it out on me. We finally had a talk about it and he "blocks out" her *bad* comments more now and always takes my(our) side and defends our family. He didn't like what it was doing to our marriage either, he just wasn't sure how to handle the situation.
I know it sounds crazy and probably like the last thing on earth you want to do, but it's an honest suggestion: perhaps you should call her just to chat. Call to see how she's doing. Tell her you were just thinking about her wondering what was new, and that you also might be moving out that way soon, though nothing is set in stone. Try placing yourself on her side - even if you're not *totally* feeling it, and you may find that she eventually reciprocates it by being on yours. AND if, you form a direct relationship with her, you will help your husband tremendously to not feel like he's the referee between you two, or the "middle man". Then you can use your own intelligence and charm to gently change his sister's behavior via your own direct conversations with her. You may even find that once you get past this obstacle, you even have found something about her you like. You will ALWAYS lose if you are against his family. Especially if your husband obviously doesn't feel the "attacks" are mean-spirited (I'm sure he would automatically take your side if he did). Assume they mean the best, talk to them both seperately. Wait for the right oppertunity in conversation to talk with the sister. If she thinks you called her for anything other than checking in socially (even if she thinks it's strange that you did) it may backfire by making her feel attacked by you (and make your hubby feel like he needs to defend his sis)- and you don't want to move closer to a mess like that! Kill her with kindness as they say!
Also, being a SAHM *can* be a VERY difficult change. It's hard to go from celebrating your own accomplishments to celebrating someone else's. It can really feel like you've lost your identity, and like a thankless job especially since it sounds like you could use a little more support and encouragement in it from your hubby. Maybe he doesn't understand that since it's not traditional *work*. Sometimes it's just really hard for guys to "get it". I have 6 kids under 10 so I understand the slave comment to an extent. I would say to you two things that I have learned from my experience as a SAHM. One, if you are feeling over-defined by your family role, it really is a serious issue. It affects your self-esteem, your *job* performance, and your relationship negatively. I've found the best way to combat this is to volunteer in the community. It's time away from the kids, you get to hang out with new friends, and you're still doing something "on your own" to make a difference, accomplishing things you can be proud of other than "Jimmy went pee-pee!" Lol :) And remember, to try and keep your sense of humor. The days the kids are really rotten and everything else is going wrong too, are days my best friend and I call "sitcom days" because if we had a video camera and a network spot, we'd be getting awesome ratings and lots of laughs! Try to be the spectator for a second before you dive back into the moment. It helps sap some of the seriousness out of the situation! Two, if you feel like a live in slave, and non a full time mom, then you need to set some healthier boundaries with the kids. It will benefit you all. Your job is not to be thier slave, your job is to raise, happy, loved, self-sufficient kids. They for sure can pick up thier toys at two and limit some of their behaviors (at least most of the time - though it may take a bit of working on until they get the initial control)Wanting to pull your hair out may just be mother nature's way of telling you that it's time to take the next step in helping your children to learn personal responsibility in an age appropriate way. Tell them no. Tell them you're busy doing your "work" and you will get around to their request in a minute. Learning to accept delayed gratification will make them more patient and you less stressed. Make them clean up their messes (at least the ones they can), and encourage them to do other things they can do for themslves. Most new skills are just extentions of ones we already have tried in new ways..it may just not have occured to them that anyone but mommy can do it.
At any rate, I wish you the best of luck in all things. If you need a pep talk let me know! :)