You didn’t word things wrong. You were really clear.
You don’t want to change your life back to make room for his kids to stay. You don’t want to be the one providing for them. That’s understandable. But it naturally follows, that for you to have him, Without making room for his kids, means that he would have to cut them off. Or at least only see them at his exs.
I am not suggesting you want him to cut them off. That’s not your motivation. Your motivation is to put your child first. But you can’t have him move home without accommodating them.
It’s ok to not want to that again. It really is. But your aren’t really blaming both him and her. You don’t want to accommodate the kids (in your own words) because of her actions. Really though, what did she do that was disrespectful? She slept with her single ex. Do you really believe he hasn’t been feeding her the ‘I want to make it work with you’ line? how come you don’t want to accommodate them because of HIS actions? Why are basing the decision on wether you want to accommodate them, on how you feel about their mother and her actions?
If you feel disrespected, then it’s him that disrespected you.
I genuinely don’t see what you see in him? He splits with you and goes back to do drugs with his ex and sleeps with her? I very much doubt he was drug free while you were together. He doesn’t really provide anything of value to his kids.
That toxic relationship? That was half him. She hasn’t tricked him. He made choices.
If I were you I wouldn’t be contemplating getting back together at all. And not because of the kids. Because he is clearly a loser. You and your child, deserve better.