Document that whole scene at school and let your lawyer know. Again, he is trying to build a case. Good job on not emailing him. Like the other poster said, just have the lawyers handle it. You need a temporary custody schedule, Karen, otherwise he will continue this. He is also trying to prove you are unfit in any way he knows how. I'm worried about your kids and what he is asking/saying to them. I think it is great you continue to do this Tuesday thing because it gives you witnesses to your mothering. He will try to prove you a bad mom. If you don't let him bully you (which you WON'T), he WILL go for full custody so be prepared for that. The writing is all over the wall.
As for your depressed time.......what you are like NOW is what matters. He could have ordered temporary custody during the time when you were severely depressed...that time is over. You are healthy, happy, and being a good mother and woman. Your pastor, friends, and children can attest to that. Even if he brought those letters to the court, it would have no meaning now. Even if he pushed it the worst they would do is have a psychological evaluation of you which you will show you are fine with. Another topic that needs to be brought up is the verbal abuse you have dealt with with your stbxh. I would start gathering that info. Because it helps show the big picture of what is happening here and the reason for you trying to need the schedule and the need to have things done through email or with a third party always present and possibly the need for the kids to be with you.