Sorry to hear that OP. My partner and I both have children, don't live that near each other, and we're trying to work out how we can live together. So to hear of the 'backwards step' as you see it, I can imagine that will be upsetting.
Is there no way you can work with him to stay?
I agree it does sound unsupportive, not like he's got your back.
I totally get it as well, as it is really hard with other people's children.
I would think he could just stay in the background, not get involved between you and your daughter, but support you in private.
Moving out doesn't sound like he's helping you at all. And with all the other pressures on you- going back to dating each other sounds like another job on top of everything else.
Would the plan be that he would stay over when you date? It all sounds a bit strange.
I admire you for supporting your dd so much, I think that's absolutely the right thing to do.
Is there any way your partner could keep living with you but he and dd don't need to interact much?