Yeah, that's the difference between you and me then. I believe Jack has a certain amount of integrity that would extend to him not taking sexual advantage of his employees. I therefore believe that, given the fact that there is a canonical relationship between Jack and Ianto, Jack would have willingly given Ianto a more leading role in their personal life, just to even out the power Jack has over Ianto in their professional life. And so I don't have a problem with the assumption that Ianto has that power over Jack, I think it's a power Jack would happily have given him to even out their relationship.

Sure. The more, the merrier. I really, really don't like Gwen as a character, mostly because I think she's an evil bitch to Rhys, who seems like a really nice guy, but if they suddenly went with canon J/I/G, sure, why not? It would seem more fitting with Jack's character, and even, really, with Ianto's as I perceive it.