You aren't going to get rid of your xh because you have children together. Even when the two of you are sitting in rocking chairs in a nursing home, he'll still be a thorn in your side. As I have mentioned before, an elderly lady told me many years ago that the only way you'll get rid of someone in crisis is when one of you are six feet under. The tie that binds you is frayed, but they can't let go no matter what.
Your xh is trying to make your life difficult because he sees that you are happy and have someone who is good and treats you like a queen. He's not happy that you are moving in w/the new man and he also sees that he doesn't have any control over you. He now knows that there is a good possibility that you may remarry at some point in time and he doesn't want that to happen. He wants you right where he left you and unfortunately, that isn't going to happen. He's going to pull out the stops and make life difficult for you by using the kids to get to you. Don't let him see you sweat!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.