I believe very much in praying for God to "dispatch angels concerning you" and I have asked for that. I ask for that daily to watch over and protect my family and my men on the job.
This is not meant to be one bit in doubt of that prayer or to demonstrate a lack of faith, but I believe we have to do what we know how to do and what we are able to do along with asking for that protection. After that we rest in God's care. My wife was in a very violent relationship before me. I know others who have been also. The thing I've learned is that most of them don't change. I'm glad they seem to be trying to get help, but they can do well for a long time and then just snap. I think you know this.
My point; if you're in a state where you can arm yourself, you should. No 911 call or restraining order is going to be quick enough if something (imaginary or not)sets this guy off and he flips out and decides to do something. At that moment where he was on your porch there was no amount of reasoning that would have settled him down. He fits the mold for what my wife went through. At the very least, get some kind of security for your home so you at least have a head start in knowing he's there. It can be something as simple as door stop alerts, window opening alerts which are cheap and will work for a non-professional like him.
I guess my motto goes something like this: Trust God, but carry a big stick.
"Unless we make Christmas an occasion to share our blessings, all the snow in Alaska won't make it 'white'." -- Bing Crosby