Could you spend some time explaining why you think this woman is a manipulator and a liar? I understand why this has been so hard on you but what I don't understand is why you aren't more angry at your boyfriend when it comes to broken boundaries. He is the one who should be looking after you and your relationship and he is the one who researched and worked on opening your relationship up.
I guess I'm just worried that you are putting a lot of the blame on this other women because things have hurt you badly and you would rather it be her fault then his or no fault but miscommunication or misunderstandings.
I don't know that to be true but I was wondering if you could get into more detail about what rules have been broken (so far they started planning for the future without you there, but no action on those plans were taken? And you had a rule about overnights that you talked about and agreed to change for a special event) and what in her and his actions have been out of line and hurtful to you.