ah didn't see the not turning up since january, but still you are living at the mercy of a guy who has no respect for you OR for authority.
This guy feels entitled to terrorise you whenever he likes and nothing and no-one will stop him.
Now he is emailing you ranting incoherent nonsense, what if you don't respond, what if he DID decide he needed to have it out with you. What IF he decides to pop round in the middle of the night? or heaven forbid on a weekend when the police are busy dealing with drunks? what then?
Why on earth would you WANT your DC to have any contact with a man as clearly dangerous as this, both to you and to them?
He gave up all rights to being treated as a normal human being when he stopped behaving like one.
I know you don't want to move, no-one would, but the way I see it, you are in danger, and there are not enough adequate safety guards in place to protect you.
If I were you, I'd investigate legally your ability to vanish from this man's life. Your DC are not going to learn anything of value from him, apart from if they look at his life as a cautionary tale.
For the very reasons you state, the courts releasing him the next day, the police not knowing where he is, I would say that the BEST and only option open to you is to move where he can't find you.
I'm sorry I don't mean to be harsh, I'm trying to help, believe it or not
I just don't understand why you would not want to be safe, why you hang onto your DC and by default, you, having contact with him.
ONE decent parent supplying the love, security, feeling wanted and safe is better than one parent living in fear and the other one causing it.
Ask yourself this question What's in it FOR ME? An abuse victim/survivor never puts themselves first, and this is the chink in our armour, this is what lets abusers in.
Please put yourself first, please don't stop until this man is well and truly away from you and can't ever find you again. Your kids will understand.