I think that he still is the Dark One in name but the Curse doesn’t have the same hold in Storybrooke as it does in Enchanted Forest. If he went back to Enchanted Forest, I think he would be the dark one all the way again.
I see Rumple’s power as being layered. He had the Dark One powers when Bae was lost but Blue Fairy told him the curse was beyond his capabalites…
Blue Fairy: Well, then I’ll comfort myself knowing that such a curse is beyond your abilities.
Rumpelstiltskin: Oh, for now. But I’ve got all the time in the world. I will do nothing else, I will love nothing else. I will find a way. You took my son, but I will get him back.
So he gained new powers in order to be able to create the curse. Maybe the the powers he has right now are those extra ones that aren’t tied into the Dark One curse. So, I don’t think even with magic in Storybrooke the dagger will be able to control him.