I had/have similar issues with my family. I avoided the problem for years, just living far away from my parents. Then, as I grew and matured and thought I had it together enough to be strong and establish boundaries, I decided that my aging mother could use some help and invited her to be my neighbor in my apt complex. Well, she was old and feeble, had cancer, COPD....so next thing I know, she's coming into my apt with the ëmergency"key I gave her, just on her whim to look in my fridge, criticize my housekeeping(you just posted a reply to my needing help with my house cleaning, so this is a sore spot with me anyway), etc. Well old mom started crying when I expressed my feelings about boundaries and respect, etc. I told her that she was not going to turn this into her being a victim. I was the one who had been violated, and me requesting boundaries is a normal thing.

So, what I'm saying is that I think we will always be particularly vulnerable to family members, and if they are not interested or maybe don't even comprehend boundaries (I truly think my mother does not) that it's just up to us to protect ourselves and our sanity. I ended up having to move away from dear old mom, so I am not so good with the maintaining boundaries with her even now. I guess you have to do whatever you need to do to stay balanced. Personally, I think I will always be fragile and have to avoid those situations for my sanity.
I hope you will find a way to deal with the situation since there are innocent people not involved with "the game". I just want you to know that it sounds like you are doing all the right things, but some people will never change.