We've been separated for years, divorced for two. He still works himself into a frenzy over any issues to do with our teen children - this week it's because dd has taken up running and apparently that's me trying to force her to lose weight and be mentally unhealthy. He basically makes stuff up and uses it to attack me and then will send reams of abusive messages calling me a cunt, attacking my character and that of my family and anyone who would have anything to do with a cunt like me 
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I am scared of him. He's been violent in the past. Not consistently, just the occasional outburst always towards me. He's an unstable, chaotic alcoholic. There's no contact order for our children in place as he disappears for months at a time then turns up demanding to see them. I just want this to stop. I sobbed in front of my children last night as this had been going on for over a week. The abuse isn't constant it comes in cycles. Usually after he's seen the kids. I picked them up after they had dinner with him earlier this week, so he got eyes on me, which seems to have set him off.
What now, reasonably can I do legally? I'm feeling defeated and desperate today. Thank you.