Start writing down all the incidents and save any evidence such as emails and text messages.
Get in contact with a domestic abuse organisation for support.
OP he's a dangerous individual, he strangled you and he's not leaving you alone which is a bad sign. You need a safety plan.
You should make sure your home is safe, get a video doorbell and you can contact the council housing department, they may be able to make your place safe. If not, fit locks to the windows, get a chain across the door and don't let him in.
Download a co parenting app and block him on your phone. Arrange collection and drop offs away from your house, either through a third person or in a crowded outdoor area.
Don't give him access if you think he'll hurt the children, you can withold contact in the case of domestic violence.
His family will of course take his side so don't worry about them.
Have as little to do with him as possible.