I believe that living with anger, creates an angry life. Showing the angry life to your kids is not the lesson you'd prefer to give them. Discharge your anger however you need to do it, but quit firing poison darts at your co-parent. You are liable to hit one of your kids instead.
Today, I have everything I need. I may not be close to having everything I want. But my basics (food, shelter, safety, community) are pretty well covered. Today I can forgive my ex and focus on my kids and their well-being.
Co-parenting is a cooperative relationship. When one of the partners decides to be uncooperative it changes the dynamics. However, as a positive parent, you can be the bigger partner. Choosing the positive is about every aspect of your life, and your kids are the most important relationship you can manage.
One positive parent can make 100% of the difference. I'm not perfect, and occasionally I want to lash out when she does something that seems unreasonable. I don't. I never do.
In spite of the anger and resentment, you've got to drop your psychological work elsewhere. Your kids don't have any skills for dealing with your sadness or anger, and your ex has got better things to do.
My ex-wife and I don't see eye to eye on a lot of things. But one thing we've kept relatively clear over the last 5 years of divorce is THE KIDS COME FIRST. Always.
I felt like I had a pretty good idea of the way the divorce was going to go, once I agreed to actually get a divorce. We went, eyes wide open, into the negotiations about parenting rights, money, schedules, and I also felt like I had a cooperative soon-to-be wife who was not going to try to destroy me. The first part was true, the second part, well...
I will be in the process of recalibrating my life in relationship to my ex-wife probably for the rest of my life. Even after the kids are off and doing their own lives, there are always collective contributions that need to be made, adult advice that needs to be given, and we will never fully separate from the relationship.