Of course he wants you back! He needs a whipping boy, an object for his abuse. And most abusive men know that finding (and keeping) such a willing victim is not easy. Think about what's involved. First they have to 'scout out' women who appear to be vulnerable. Then they have to put on their 'nice face' and work hard at hiding who they truly are. It takes lots of time (and money) to bamboozle a woman into the position you've been in for so long. Neither of which he wants to expend. He'd rather just have his already conditioned victim back.
But you aren't going back. You've already come too far for that. It may not feel like it, but you are way beyond halfway in your journey away from him. I'm not talking about the legalities. I'm talking about the fact that you now see him for what he is. That's more than half the battle. What remains is strengthening and hardening your ability to ignore his abuse. And you're doing that, too, although he still gets to you more often than he doesn't. But that will change. There are so many many threads on MN of women who have turned that corner. You will too.
Both of your children have mobile phones, yes? If they need you they can contact you directly. So you can block him. Or you can just tell him (and the DC) he's been blocked. He won't know if you do or don't block him. On the flip side, I know that although those texts are demoralizing, the judge will see them for what they are, evidence of his abusive behaviour. Have you spoken to your solicitor? I'm sure there are steps that can be taken legally to prevent the abusive messages and/or make all communications go through your respective solicitors.
Is there any way you can get yourself a new phone and number? Give that number out for your day to day needs and keep the old phone sitting in a drawer in silent mode and check his messages only once a day. Now, obvs you won't be able to give the number to the DC, but you can check for their messages more often without reading his. I know those nasty messages will still be there, but at least you won't be hearing that 'ping' all throughout the day and continually reading his abuse as it comes in. Instead, you can check it once a day, at a time of your own choosing when you are mentally (somewhat) prepared for it.
As another option, when BFF was divorcing her ex used to send horribly abusive emails. She'd put all emails from her ex in a folder, unread. I'd read them and let her know anything she needed to know but wouldn't pass on anything abusive or nasty. Maybe you could do the same with your phone. Leave the messages unread until someone can read them first and just pass on what you need to know.
As far as when will it come to an end, that part of it IS in your control. The answer is when you get to the point where he can't get to you that way. It was an epiphany to me when I realized that although I cannot really control another person's actions, I can 100% control my reaction to them. It takes time and effort, but it can be done.