Here's another update and its a big one.
Last night, her coworker and I met in a bar to talk. Originally, the plan was to meet solo while my fiancé has her girls night out, but circumstances changed that a little. He had injured his foot over the weekend and couldn't drive, so my fiancé dropped him off at the bar. Since I was delayed in traffic and she was anxious how things would turn out, she decided to stick around until I arrived. When I did, they had already ordered drinks so it was the three of us for about 45 minutes. During that time, we talked relatively freely about nothing in particular, basically having a friendly conversation. I am pleased to say that my insecurities and agression towards him were gone and I felt rather comfortable even with the discussion ahead. Whatever happened that night, I had resolved that he was no threat to me any longer.
During that discussion I discovered what my fiancé had been bursting to tell me but felt she couldn't because she believed it wasn't her place. At some point, he (accidentaly) used the phrase "my fiancé's daughter" which made me almost jump in my seat. Turns out he is engaged himself in an open relationship that is fine with sex and BDSM outside their relationship. At the very least, this resolved the "in love with my fiancé" issue, though I still asked him later and he denied it believably.
After she had finished her drink, my fiancé took off and we started talking seriously. I started by telling him that his behaviour tonight would determine wether or not there was a future for their friendship but I also told him that ultimately this was not my decision but hers. I can ask her to break it off, but only she actually can make that call. She had told me before that she would if I asked her and he told me that she hald also told him this. I also apologized for threatening and bluffing him, feeling that I had been wrong in doing so.
I proceded to tell him that I believed that they had cheated on me and he had behaved like an asshole. I also told him the realization that my initial reservations and prejudice towards BDSM were a transfer my mind had made. If BDSM is evil, my fiancé is a victim and she didn't cheat on me. The same mechanic seems to have been at work when I gave my permission(s) for their games. If I have consented, it was a choice and not cheating, hence I have no reason to be hurt. (Yeah, my mind works like that. It just takes some time to figure out the signals my instincts send me.) Before I could finish he started to basically tell me what I had wanted to tell him from his point of view, in essence proving that he arrived at the same conclusions I did and seemed to genuinely feel sorry when he apologized.
Here's how it went from his point of view: He had been hidding from his sexuality for years until he was finally introduced to it. When he had his comming out, he felt so happy and fullfilled that he began to resent the time he spend hidding from himself and the prejudice he harbored that kept him from exploring. When he felt my fiancé to be in the same situation, he basically turned his active thinking, safeguards and better judgement off, telling himself it was for her benefit. In short, he believed to be saving her from herself. (at this point I wanted to beat him, but managed to restrain myself and continued to listen.) However, after meeting me and spending some time thinking on our encounters, he discarded his initial feeling of righteousness that he had based on my lack of understanding and prejudices and came to realize that he was in fact deluding himself and that he went foreward because he couldn't stand the situation. He had put himself in her position and transfered his past desire to be "freed" onto her and due to this, felt justified in moving foreward. He realized that he had not been acting for her benefit and well being but for his own and that he had been wrong to do so.
Ultimately, he accepted the responsibility for his decisions and apologized for them. Then he earned my respect by offering me, without any promting, to say the word and he would disappear from her life. (This weights doubly considering that his fiancé lives in town and he was just offered a permanent position in their company. Currently, he is still a freelancer with them.)
Furthermore, from his point of view, now that my fiancé and I have started experimenting and he has realized that he overstepped his bounds, he feels no desire to keep up anything else than a platonic friendship to her. This is due to both the fact that he knows that I am not cool with it and that he feels no further desire to play with her knowing how he overstepped his bounds and deluded himself. (He basically admitted he had in fact been unwilling to listend to anything I said in our prior encounters, because he had written me off as a prejudiced asshole unable to understand a word he said. He apologized for that too.)
After this, we continued to talk about BDSM and sexuality in general, sharing opinions and how the story went for each of us individually. I told him of my suspicions that he was not as experienced as he made out to be and he basically agreed that while he was booksmart, many things that had come up in the past two weeks had never been an issue before because everyone had always been on board so far and none bothered with the finer points and understanding. When I eventually dropped the bomb with the orders issue he seemed genuinely taken aback and when I asked him if he would be fine with revoking each and every past order in my presence he agreed immediately. Upon seeing his face and gauging his reaction, I felt this was unnecessary and dropped the issue both in discussion and as a fear of mine.
We continued to talk for quite a while but to make a long story short, either he is the world's greatest con artist, in which case he deserves to have fooled me, or (much more likely) I have finally managed to break through to the real person. Once there, I found he was a rather likeable fellow. Eventually we called my fiancé to join us and I dropped my reservations towards their friendship, feeling that a basis of trust had been established on fertile grounds. We continued to talk until closing time before dropping him off and going home.
I has been a while since I slept as well and sound as I did this night.
It'll still take a long time to establish real trust, but now I feel confident that the immediate issue has been resolved and that we all have come out stronger for it. This would not have been possible without this board as both a vent for me and a source of advice and support from you guys and for that, I wish to once again thank you from the bottom of my heart.