I know how you feel. My mother is very manipulative as well, and knows how to work people. I'm the only one that will stand up to her, and for the longest time, whenever she would get in one of her "moods", I would be the one the family would call to get her out b/c I was the only one that could. The way I did it was through fighting with her. It was emotionally draining, but it worked. However, that's not working now, and it looks like she might be suicidal (but I can't really tell if she is, or if it's just a ploy to manipulate us). This is mentally (and becoming physically) exhausting for myself and the rest of the family, so believe me when I say I completely understand the feeling of wishing "she would go away". Right now the family is talking about having her committed (well I started that conversation and have been doing all the work). At times, I think we should, but at other times I think we shouldn't. Part of me wonders when I don't think we should if its b/c if she did commit suicide that it would be over we would finally have some peace.

I know I'm rambling, and I don't want to turn this into something about me. I just want you to know there are people out there going through similar issues, so you're not alone. Hang in there.

The subject line in your post is "What now?" The answer is "Move on." Do not allow any one to lay an unearned burden of guilt on you. You owe nothing. PERIOD!!!
You have a family - your children and a loving husband who is empathetic because he has experienced your world - he with a former wife and you with your mother. The specifics of your experiences may differ, but the view is the same and the baggage matches. While it is accepted that it is easier to walk away from an ex-spouse than a parent, it is equally necessary to walk away if you want to give your family a better life than the one you were given. If all of these other people in the family think that they have the answers, let them implement them on their time, their dime and - most importantly - their premises. If it means that you have to walk away from all of them, then so be it. Look ahead, not back. The penultimate payoff will be a rich and rewarding life with the family that you and your husband have built, the people to whom you owe a bright future with a happy, well-adjusted wife and mother who can devote herself to her present and future, not her past and a recurring nightmare. Believe me, this is a cancer that will consume you if you don't learn how to pronounce the two most difficult words in any language: "No" and "Goodbye".
I wish you strength, clarity and decisiveness. You will be in my prayers.