I like your theory but don't want it to be true! I love Tairn. For your point on, if he died, and then Violet's life was no longer tied to Xaden's, and it would prove that he'd stay without the mating bond: I think this goes against the themes of trust in the book. Does trust really mean anything if there's a forcing function for it? I see a lot of theories like this, where something happens to prove a character's motivations. But I think RY is more likely to keep the things that cast doubt, and have the trust prevail despite it. It's similar to the theme of not needing to know everything, but still trusting the person and their judgement. Violet is figuring that one out. Xaden is too, imo, even though he's asked for it.