WTBH- maybe the extra chances you gave him were in some ways necessary so that when the order is enforced, the girls truly KNOW what happened and that they can't count on him--so years later when he talks about how you kept them from him, they will know it's not true.
I have many of the same feelings about what I've done "wrong". Now I battle with feeling "wrong" for enforcing my parenting plan in ways that keeps them apart. We can't win.
You're doing an incredible job and your kids feel it. Don't beat yourself up over trying.