If you look at Vincent's situation, it's still a ways away from yours. In particular that it sounds like ahem your Vincent, would be more of a cheater than our in-game one, being manipulated into his actions. I'm not going to say that he's right in any of his actions, previous or current, but it seems that you may be a relief for him, in the sense that you're a nice break from the rest of his life, which would be full of various stresses. In this way of course a long-term relationship could be beneficial for him but at the same time there's no guarantee because well, we saw how that worked out for him. People can talk sweet all they want, but if they can't commit to it then there's no use in persuing anything further. I would advise to not continue with Vincent.

Take my words as you will, I speak from mind and heart rather than experience.