Jumping in, I have been folowing your sitch as well and it has given me great understanding about the other side of the fence.
Anyway, as far as the being at her beck and call, the first way to get out of that is to GAL. Start taking classes on evenings. Cooking class, photography, kung fu. Have a set workout schedule and DO NOT DEVIATE. Whatever. But have firm commitments in place so that she can't "guilt" you into anything. Be kind and understanding and just say that you need more advance notice if she wants you to watch the kids.
And then be sure to talk about what you learned to your kids at least so she will know that you aren't just gallavanting around town when you say you are doing X,Y,Z.
You are going to make it through this. I know it is hard but start making plans. You HAVE to GAL in order for you to detach and truly go dim or even dark.
Good luck, and I am rooting for you even though I may not respond to each post.
Many hugs.
You will come out of this a better stronger person. Trust in that.
