As PP said, he’s abusive. It’s all on him. None of this is your fault and you do not deserve to be treated like this. Contact women’s aid for support because from what you’ve said, I would expect him to continue to abuse you post separation.
Block him on phone, email and social media. Report his abuse to the police and get women’s aid to help you navigate a non mol and an occupation order.
I don’t know what age your son is but I’d imagine he’s going to use child contact as a way to continue post separation abuse of both you and your son. Tell the school what’s happened and find out what support they can offer to your son. They might be able to provide some counselling for him because it sounds like he’s been a victim of your husbands verbal and emotional abuse too. And he will have witnessed your husbands abuse of you. This is very distressing and damaging for children and he will benefit from getting some support.
Once you get a non-mol, have the locks changed so he can’t access the house. Put up a ring doorbell so record if he comes to the house and you can report him.
Please get a sexual health check because he has been sleeping around and put your sexual health at risk.
This book will help you see some of the tactics he’s employed in his abuse of you. It’s free.
https://www.docdroid.net/2fZmz40/why-does-he-do-that-pdf
Only communicate with him about child contact via a parenting app if you have to. Do not get drawn into anything. Learn the grey rock method and employ it.
https://psychcentral.com/health/grey-rock-method
Please contact women’s aid today. This man is vile. He’s highly abusive and he sounds unhinged. They are the best place to get support and advice on how to navigate this situation for you and your child.