Breaking with him
Thank you so much for the support, it's very appreciated. I've been the secondary in a casual, dating V, and it was great. I've been the secondary in a triad, and it was great. I've been the primary in a triad, and it was great. In a polyfi V where deeper emotions are involved, it sucks (at least for me).
Fortunately, we aren't living together. They did ask me to move in, but I declined because she and I weren't getting along, and I had a pretty clear idea where it was going. Once I declined, things got even worse, actually.
Honestly, everything triggers drama with her. I'd love to give examples, but I'd rather not be too identifying. The closest I can get is that instead of just saying "I really could use someone to support me right now," or something adult like that if there is a work or family crisis of some kind, she'll start wailing louder and louder, in increments, until someone comes to soother her. Which, incidentally, I don't do because I am not interested in reinforcing that. Which may make me a bitch, but really, I don't do it for anyone. Ask for what you need, and I will give you everything I can. Act like a spoiled child, and you've totally lost me.
She's very emotionally manipulative and immature overall; and, you are right, he's used to it enough he kind of assumes everyone would be okay with it. Weirdly, I am better at dealing with it very short-term than he is, much like I would be with a child; but, there's a reason I don't have kids: I don't want to deal with it on an ongoing basis. He, however, deals fairly well with it as a long-term thing. And, in some ways, perhaps he needs it? She and I are complete opposites in terms of personality, which I know fulfills very different things for him (because he's told me this). She's also single-white-femaled the hell out of me, which stains things. She's now trying to replicate me and the things he and I do together that she's been very uninterested in (and sometimes even outright against) before me (not in bed--we're all VERY adventurous there--but IRL), which is just plain weird.
I am struggling with the when and how to end it. I don't want to end it, really, because I love him. When we are together, it's euphoric. We're so well-matched in so many ways, and we have an amazing time together. We compliment each other, challenge each other, and I haven't felt so strongly about someone in a very long time. But, Reality Happens, and I need to be in a healthy place.
I keep telling myself that. But I still haven't ended it.