Rule #1- DO NOT TELL YOUR DH you want to disengage!

Yes, disengaging can save your sanity. You just have to figure out how much you are willing to let go and how to start. I honestly would say the Serenity Prayer a lot when I first started: "God grant me the serenity to accept the things I cannot change; courage to change the things I can;
and wisdom to know the difference." - Religious or not, accepting the things you can't change or that have become too much, Standing up for yourself and demanding the changes that have to happen in your home and the wisdom to know where to fight and where to let things fall as they will, this prayer is disengaging to me.

My first step had to to with behavior. When the school called I made them call DH. When he acted up at home I would remove me and my bios from the room or situation. DH noticed, it was a series of big fights with us. In the end, he is a better parent because I have disengaged.

Obey rule number 1 as quoted above - don't tell DH you are going to disengage - it gets them all defensive and is like us throwing down the gauntlet. Read this: http://www.steptogether.org/disengaging.html

Start gradually and just drop doing things you were doing before, so that DH HAS to step up. If you babysit his kids, tell him you aren't doing it any more.

You can disengage as much or as little as is appropriate for you, it is a lot easier if you are non custodial and the kids are not little. We have SKIDs EOW, and I disengaged after my first year with DH. If your situation is similar, feel free to PM me with specific issues.