Yup, I have a post over in “The Doctor” about how both Rumple and Regina were manipulated into their roles by another individual. Doesn’t absolve them of their choices and actions, but it certainly makes both their stories more tragic to me, at least.
Did Rumple fully realize what being the Dark One would entail? Probably not. Re-watching that scene, it’s striking how completely Zozo preys on his fear, panic, and adrenaline by goading him on, questioning Bae’s paternity, telling him that he would never have the courage to control the Dark One. And even before that Zozo finds him at his most desperate state, when all his other options are gone, and preys on his desperation. Also, it’s striking that Zozo gloats, “looks like you made a deal you didn’t understand.”
Given the absolute change in demeanor from that scene to the next, I’m fairly convinced that the curse exerts some sort of influence on the person it’s attached to. I imagine it’s similar to the Horucrux on Ron in Harry Potter, or the Ring, or Dexter’s Dark Passenger (I always seem to understand works through referencing other works 🙂 ) Yes, he still has free will, but his decision-making is severely compromised. If a redemption story is in the future for Rumple (which I hope), I imagine that the more specific mechanics of the “Dark One” curse will be revealed insofar as how deeply it affects/alters judgement and personality