I also wanted to add:
My relationship with my fiancee is very good. I might not have been clear on that in the initial post but I had a lot to say as it was.
Also, the first male in question isn't really an asshole. He is simply a very sensitive person and I think he could never be involved in a polyamorous relationship, putting aside the fact that he and I shouldn't embark on one (for reasons I won't get into, but we can't). I guess I am just looking for others' thoughts on how to move past sexual feelings, or potential ones, in friendships where the potential for "more" is known or possible.