Well, I have a weirder version of what you are going through, but no less tragic.
I was in a MFF triad for about 4 or 5 months. When it was good, it was great. When it was bad, it was horrible. We all wanted it to work, but there were so many issues. The biggest problem was that both of the women had multiple personalities. So there were lots of complications.
One of the women, who I was with first, was really into it half the time and resented it the other half. She was not very in touch with her alternative personalities and changed a lot. She did not want to get help on it. In the end, it broke us up.
I formed a relationship with the other one. It was a nasty break-up. However, years later, I was talking to her and she wished she could have worked out after all.
The relationship with the other woman lasted about 2 more years. However, we still had problems dealing with her personalities. We talked about polyamory, but I didn't think we were stable enough. We tried it. But it was more of a way for her to find a new relationship and move out.
Not sure if that helped, but figured I would offer it anyway.