My advice is two words: PAPER TRAIL.
When my wife first threatened me on his behalf in June, I filed an incident report with the Sheriff. I wanted a paper trail. When she threatened me again, I filed another one (I went to the Sheriff’s station to do this).
So, at the beginning of the month, when he did hit me, I had not only the police report from the battery, but two threats made two months earlier to substantiate the danger. I had pictures taken immediately afterwards, and paid a visit to the doctor who wrote up a nice report.
Document the fear of physical violence. The penal code considers fear “force”, and therefore by creating an environment of fear, I think you have an argument for harassment.
If he has a criminal record, what is it for? If it is a violent crime, you are the children’s father and you have the right to express concern about their well being. If the judge refuses your request, ask the judge to recuse themself. That throws them, it basically says that they have to admit that they can’t hear the case. Most judges’ egos won’t let that happen, so they may reconsider. I actually did it with an appellate court judge on a panel of three. And he left!
I can’t stress it enough, document everything. And where and when possible, have a third party document as well, because that lends clout.