He was awful last weekend. But worse to your children.
He threw clothes at your child ( clothes this time )
He is fine with the younger ones but awful to the older ones.
There is nothing about protecting your children that anybody should be able to minimise. Wether she was having a bad day, or had an opinion, or possibly just put the phone down from something horrific, don't let her tone distract you from your duty as a mother and UK law, which has a very clear view on failure to protect. He is already causing trauma.
You need to also sort the puppy. If he can't be trusted with children he can't be trusted with one that can't talk. Try cinnamon trust for foster. You may get housed quite quickly, it's the smaller places that are thin on the ground, and women fleeing DV get top priority. Just be prepared to go anywhere.
Good luck OP, your doing amazing. You CAN break this cycle, show your kids what needs to be done. You sound like a strong woman. Take your life back now. You have taken steps that other women sometimes can't and they are the right ones. Don't hesitate to reach out if you want a chat. 🙂