Don't know is a problem.
You know this situation is damaging you.
You are starting to realise that it must be damaging DD.
He has told you he wants to remain an addict.
Your situation would have most women running for the door.
I think you know, at some level, things have been bad enough for long enough with too little sign of change, that leaving is almost certainly the right thing for you and DD, at least for a while until he gets clean.
Yet, you are blocking yourself like mad. It is like you are desperate to talk yourself into staying.
Things are bad enough to leave today already by any normal understanding, so you can't hide behind "if things get bad enough, then I will definitely get DD and me away"
Until you understand your own issues and tackle your own crazy dysfunctional thinking then you are stuck. He could get much much worse, damage you and DD even more, damage himself even more, and you will find a reason to stay because what's keeping you there is something in your own head, it's nothing to do with his behaviour or the impact on you and DD (if it was, you'd be long gone).