Op hugs. It's shit I know but it does get better.
The best advice I can give you is to make a decision to not emotionally respond to him. My ex is a cunt. He made my life miserable for about 6 years by either demanding, criticising, abusing the then free legal aid system which I had to pay for as I was working, letting dd down, not paying csa when he was working, threatening and intimidating.
In the end I just thought 'fuck it'. Told him when dd would be available which matched the court order, told him I would change it if she wanted to do something different, told him I didn't give a fuck what I thought about his opinions as I was raising her in the way I decided and if he didn't like it to take me to court.
Now dd is nearly 13. She sees through him and knows what he is. We have spent the last few weeks deciding on a plan for her to reduce contact from 2 nights to 1 night eow as she doesn't want to go. But doesn't feel able to tell him. So we have invented an afterschool activity she must do on a friday to support her gcse and a youth club she will be at until 8pm. As he doesn't drive it will be too late to collect her. And she wants picking up at 1pm sunday so she can 'spend time on her coursework'.
It does get easier. But you have to remember he has no control over you anymore. He is the father of your dcs but that's it. And if there is abuse you don't have to go to mediation. Ime it was a waste of time and just another way to try and control me. Our mediator stopped the second session half way through as my ex was so vile and told me separately she would recommend to the court that we had no more sessions due to his behaviour.
Just remember your dcs will know when they are older what he is and what you are. And he has absolutely no power over you.