I need to add something here...
You stated that your ex showed up at your kids' practice; that you saw her there and didn't confront her there; that you calmly packed up your kids in the car and then you left the car to make a phone call to your ex; and that in that phone call you insulted your ex and told her to go < edited > herself.
You have also told us that you regularly battle her on medical treatment for the kids, regularly send her emails criticizing the way she parents, you have told us that you email her regularly telling her she's in violation of the parenting plan and use the parenting plan as a method of controlling her behavior.
Then, you say that she set you up.
Man up. Take responsibility. You say you take responsibility and then a few posts later imply that it's all unfair and you're a victim of a biased system. Maybe, but just from the little you tell us, when you're trying to present yourself in the best light possible, you've shown yourself to be a complete, controlling, < hindquarters >.
Stop referring to your ex as "the NJ". Refer to her as your children's mother. Refer to her as your ex. But stop referring to her as NJ. Change your outlook and your attitude. You've lost the right to blame their mother for turning your children against you. You've lost the right to claim you're a victim. You need to show up hat in hand and apologetic. Did I interpret your post correctly that even the school thinks you're bossy and controlling? You've got to fix things, man, and all that starts and ends with you.
People who live their lives watching only the rearview mirror tend to crash their cars. - Trevor