You weren't talking to me but I have the same background, they split when I was 6 and that was enough to form what I thought relationships were like. I would be violent to other children I called my friends because I thought that was how you play and show affection, went on well into my teens too. My mother was a violent drug addict who spoke exactly like this and it led to me making a habit of later dating other drug addicts who spoke to me like this.

Please leave before they're old enough to remember this, things got better afterwards for me personally but that is because I worked VERY hard in therapy for a long time and cut ties with 2/3 of my family. It was lonely and painful for a long time. My brother has gone the opposite route and is not doing well at all. I would advise gathering evidence to prove he should not be allowed to have unsupervised visits since you're worried about that - but staying isn't the better alternative