Two secrete issues here.
The contact and the dv.
Contact needs to sorted through a solicitor/mediation centre agency.
You can ask for supervised contact, third party drop-off etc.
They will also see how the visits affect your dcs.
He dv needs reporting to the police. Now.
Keep all the awful messages, they are your evidence!
With those messages, it should help your case for him to have minimal supervised access.
If he manages to turn up to a supervised session, he might spend a couple of hours playing or doing something useful with dcs, that they might enjoy.
I have to admit to being a bit biased here. My ds does not want contact with his dad.
(Boring, grumpy, shouts all day, eats crap without feeding ds, smashes stuff up, lies, changes his opinion constantly...this is what ds has noticed, not me!)
We had a couple of visits after we split. Xp spent all his time being physically attached to new GF, ignoring ds.
Xp now can't be bothered to see ds, as I won't travel for 90 minutes to visit them.
We saw a solicitor, first hour was free. She said...
The parent who move away is the one to travel to the child's location.(unless they are going to an event, asked for by child etc)
He should be paying 20% of his income to support dcs. (20% of too lazy to get a job isn't worth claiming for...)
He is supposed to come and visit about once a month or sort of every half term.
Last year, started demanding that I took ds down to him to stay every weekend.
This was swiftly met with "sorry, I can't afford the petrol. Ds has swimming lessons at weekends, along with homework. You live in a dirty tiny house, ds has said he does not want to sleep on that awful sofa. And the only activity you offer him for the whole weekend is playing in your local park. If park is on offer, he would prefer the one with his friends in! "
Be strong. You are not alone.
You just need to find your support.