I don't think you are talking about a triad necessarily. I have had a similarly confusing time coming to grips with the relationship that as a mono I can have with my metamour. It can be close without being sexual.
Anyway I have very little time but read my last post (which isn't because I've decided to keep my blog going). That post was written when Z's OSO came to stay. It wasn't nearly as painful as I imagined it would be. We had a lovely time together and it allowed everything to really settle for me.
It will be fine.