Of course you're not perfect. Of course you feel like crying. Coffee's right on target, though. They do know where the stable parent is, the one they feel SAFE with, and that's important to children.
Your AH WILL use the children against you. Expect it. Think about how he's manipulated YOU, and these are innocent children. He'll tell them bad stuff about you. He'll do all kinds of cool things with them. He won't discipline them as you do. And they'll think; "Dad's so cool!"
But kids are smarter than we give them credit for. When they really need someone to depend on, which is most of the time in life, they'll come to you. After Dad promises 19 things, and delivers on one... or none... they'll know.