I have to agree with Freedom. What he said has given you a clue what his parents and he have been talking about. Sounds to me like they're just waiting for you to do one thing that they don't like and then they intend to make life hell for you. It might be time for you to change the rules and tell him your lawyer will do the talking for you. Make sure your lawyer knows everything he said about the false charges and the intent to drag things out just because they think they can. They may have all kinds of ideas of what they can do, but a decent lawyer will set them straight in a hurry.
I went through a very similar divorce many years ago, so I know all about vindictiveness and control freaks. It doesn't end when the divorce is final, either. It will continue until your son is an adult, so it's best that you make sure your attorney is a good one who will fight for what is right. I'm so sorry you are dealing with this. People like him, and especially his parents can make life extremely stressful, so please, don't let them bully you. They'll find out soon enough that they can't do everything they think they can, and once you have it in writing, they'll be forced to back down. Mega hugs to you. (((((aah)))))