"The thing for me is that it only ever really happens once the kids are in bed. They may or may not hear it at night".
Sound travels; they hear the raised voices if not all the angry words.
Stop minimising this for your sake now as well as your children's.
What do you get out of this relationship now?. I would really appreciate an answer to that question.
Ask yourself this as well; what do you think they are learning from the two of you about relationships here?.
Look too at the rubbish example his parents set him (as did yours).
What do you want to teach your children about relationships; this frankly awful example of one?. You want to teach them that a bullying male is their norm as well?. You are showing them that currently at least, all this is acceptable to you. You cannot fully protect them from the reality that he is abusing you and they are seeing this as well.
Your children will not say "thanks mum" for staying with someone like this and will be likely to despise you as adults if you were to choose to stay with him. They will call you daft for doing so and your own relationship with them could be ruined, they certainly won't want to visit their parents very often. They will also see you as putting him before them.
And no he is not a fantastic dad either; women in abusive situations tend to write such guff and lies when they themselves can write nothing else positive about their man. As is the case here.
Your children I would argue are actually very quiet and compliant around their dad because they do not want to see him off. They see all too clearly how you are treated and it affects them as well.
You cannot change him but you can certainly change how you react to him.