Oh dear, I too think you're making a very bad decision (shock horror!). But raging at you isn't going to change anything,
When it gets bad I hope you feel you can still post on mumsnet and get some support to you and your little girl out.
And I'm sorry but it's a when it gets bad, not an if.
I tried to overcome my stbxh' demons and battles and tragedy to get us both to the other side, to have that happy ever after dream, and it doesn't work. But you won't believe it until you've finally learnt that yourself. I hope you're one of the people that learns. The people that don't learn are the ones still lying and pretending years and years later. They're the ones whose children don't visit. They're the ones whose children got taken away... the ones their children needed protecting from.
I really hope you're not like that as it's so achingly sad, such a waste of a life. A waste of their children's lives. All for nothing as no matter how hard you try, or how much you sacrifice for him, you never ever get that happy ending.
You're clearly not going to do anything to stop him moving back in and you're clearly going to accept however worsening behaviour (as it will get worse).
Maybecan you spend a few minutes thinking about what will be your breaking point? Not the pretend 'I won't stand for it' guff, but the actual one? I think it's pretty clear he'll end up smoking more dope, and smoking in front of your DD, and you and he will get back the screaming arguments (which you'll blame yourself for), and the money will go on him, not your DD again.
But what is your breaking point? If he tries to strangle you again? Hits you? Trouble is he's done that before & got away with it, so it's easier for him to do it again without any consequences, so I'm not sure it would be your breaking point really.
What about doing any of that in front your DD? Would that be your final 'no'? Your breaking point that gets you to act?
Or if she goes beyond swearing this time? Maybe hitting and strangling other children in the playground?
I'm not trying to be mean, I'm trying to get you to think now, before all the abuse and neglect starts again, what are your boundaries? I don't believe most of the stuff you've written here, because you're trying to say the right things, to us and to yourself, and your behaviour doesn't match up with the words. I think it's important for you to recognise what's the hopeful fantasy stuff and what's the real you and the real reactions you'll have.
Good luck and I'll be here to post when you need help again, like a lot of others...