I've got a couple of questions as well.
First off, how can you expect an "open and honest" relationship with someone who was cheating on his fiance with (at least) two other people, and who lied to you about it in the beginning? i guess I'm just not all that sure how you can expect honesty.
Second,from what i understand, you have never met the fiance? I'm not really sure how you are convinced you all could live in a triad, when you don't know the fiance, and she already doesn't like you.
Look, i'm not going to tell you you're wrong, or bad, or whatever, but i am going to tell you this is a seemingly bad start from I've heard.