So if you know those things about yourself, what are you going to do?
What I see is, when the going gets tough and the spotlight is on you to change, you go to your default position like this: "But that wasn't very nice, so I simply sent back "Another boundary is that I won't argue over email. Obviously, you have concerns, so you're welcome to call me. The boundaries stand. Have a nice day." You continue to engage.
Why? Some boundaries don't need to be stated and once you've stated a boundary you don't keep restating it.
But you have to have this contact with her and this is all about you. You need someone to rescue and when she seems to be moving away, you poke her with a stick and then she does what she does and you are again the victim and the cycle starts all over again.
As I said, it only takes one person to stop that but you have to really want it to stop.
And while I understand that you're concerned about the step-children, showing them a healthy R and/or healthy communication could be the most helpful thing you could do for them.
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss