You are not his nurse, or his savior, or his support. Your responsibility is for you and your children, that's it; not your ex, not your partner, not your partner's kids, not your partner's ex. You and your children, that's it.
It feels like you're doing something wrong when you cut him off, but you can't save him - he has to save himself.
We need to reframe what is truth - and the truth is YOU are the most important person in your life. You need to take care of you before you can take care of other people.
Take some time to give yourself what you need. Just be still and be quiet. Let yourself go deep and find the answer. Your truth, the answer that you need is inside you.
Some people just aren't ready. When you feel that someone isn't ready, just let them be.
I'm not saying you never talk to him again, but he needs to prove to you that he can save himself - that he HAS saved himself. You tell him, "Do your work, and we can talk when we're a little further down the way."
Maybe that interaction will change them, maybe you letting them go is what they needed to change them.
You don't give him your heart or your energy until he's stepped into his role as a man.
We have more than one Soul Mate. That feeling you're having that seems like it's the only one, you're just feeling for the first time a deeper soul connection that you've ever felt before. And that's beautiful - it's showing you what's POSSIBLE, but that doesn't mean HE'S 'The One,' it's just showing you what's possible.