Welcome to our forum.
Venting helps. We're definitely willing to listen, and offer support. I have to apologize because I took so long to write this post it is "one post late," so some of it might be backtracking. But I want to get it out there without too much more delay for revisions.
I'm hearing you say you need advice on ways to remedy the crazy situation, but when I read between the lines, I think I hear you say, "How can I get BF's wife to go along with what the rest of us want?"
That question is complicated on a couple of levels. First of all, you can't just "change what someone consents to;" there's no magic wand for that. You can't even directly change what you yourself consent to, as consent is largely an emotional animal. One can choose what to do *about* one's emotions, and some of these choices could be directed at altering one's emotional *environment.* This could include selecting different people to associate with, or working towards removing oneself from a difficult job or locale. It could also include practicing more constructive thought patterns than what may have been a force of habit in the past. But what one can't do is push a magic button that says "change emotions," and presto, emotions are changed. "Changing emotions" is a complex and indirect process.
Secondly, it sounds to me like BF's wife has some pretty deep-seated insecurities that are driving her unwillingness to consent to what the rest of the quad wants to do. She is obviously stressed out about what she perceives as her "probable inadequecy in the bedroom." On some level, she suspects that you're a better lover than she, at least with her husband. Where does this insecurity come from? Why doesn't she have confidence in her own bedroom skills? Is it an event in her past? Something she observes when the four of you play together?
Or maybe, the bedroom insecurities are just a symptom of even deeper insecurities that she's just not as good of a partner to her husband as you are, that she's somehow "less adequate" as a person and "less deserving of love." If she lets you run off to be alone with her husband, I'm wondering if she doesn't fear that he'll decide, "Hey, being alone with Indygirl78 is much more enjoyable than being alone with my wife, so I think I'll kick my wife to the curb and stick with Indygirl78 instead." Certainly this is an irrational fear, but emotions are frequently irrational. The question is, where are these emotions coming from? They seem to be deep and very visceral.
I think you need to increase and improve the quantity and quality of communication with BF's wife. You need a deeper level of trust with her, so she will start to feel free to tell you things that she wasn't even previously aware of herself.
Usually we think of talking when we think of communicating, but actually, listening is the biggest and most crucial part of communication. Listening is an art and a science. Most people listen in a superficial way. They're hearing the other person's words, but what their mind is doing with those words is formulating a snappy retort, or just mulling over whatever they want to say when they get their turn. They're "impatiently listening." They're not quieting their own mind so as to hear the other person's words coming from the other person's mind.
You need to really get inside BF's wife's head. You need to develop a very special sense of empathy and compassion for her. As hard as it is, and as frustrating as it is that she just seems to be trying to thwart your desires, you need to try to truly get yourself into her shoes, feel what she feels, and understand why she does the things that she does.
Sometimes it helps to "repeat back" to the other person what they just said, only in your own words. "I'm hearing you say that ..." and if they say, "No, that's not what I mean," you try to ask questions to get yourself on the same page as them. If they say, "Yes, that's what I mean," your next step is to express sympathy. "I can see how that would be really difficult. Is there anything I can do to help?" After all those bases have been covered, then and only then do you "take your turn" and express how you feel and see the situation. By taking the time to show that you really hear and value what they are trying to say, you earn some of their trust and help them feel more willing to listen to what you have to say when it's your turn.
And of course, maybe you've already tried all of these techniques and it just doesn't seem to be getting you anywhere. Communication is a hard skill to master. Language is complicated, and then of course add tone of voice and body language to it. I think it would take, like, a million years to really master communication. In other words, we will all need to keep practicing and learning more about it for the rest of our lives.
Look for books on communication. Do a search (or better yet a tag search) on this site for the word "communication." See what you can learn offsite about communication by googling it or what have you.
Perhaps your strongest resource here is the ability to post and interact with other members on this site. Try to describe more in detail what it's like when you try to talk to BF's wife. See if you can really give us a microscopic view of the bottlenecks you run into when you're trying to reason with her. Share with us exactly what you have and haven't tried in order to reach her. The more imformation you can share with us, the better the odds that one of us will say, "Aha ... I just saw something new you can try that might help."
Most of all, exercise as much patience as you can. I have a feeling that this won't be a quickly or easily solved problem. It will have to be tackled in tedious, painstaking steps.
And the worst thing is, you still can't guarantee that all this effort will get you what you want. As I said in the beginning, we are essentially talking about BF's wife's consent, and her consent is hers alone to give or retain. Not only that, but even if she *wants* to consent, the emotional chasm between here and there might just be too formidable for her to get across. Sometimes people have damage that takes longer than one lifetime to heal. In which case, have extra sympathy for her because who knows, somewhere deep inside, she could be suffering more than anyone could ever know. Just because she's good at subliminating all the hurt and fear, doesn't mean it's not in there somewhere. As I said, I get the feeling that she is experiencing some really deep insecurities, and we definitely haven't gotten to the bottom of them yet.
I know this all may not be quite what you wanted to hear, and may not be as helpful as you had hoped. But anything that helps even slightly right now, may lead to other posts in the future that will help more.
I am certainly pulling for you, and sympathize with your situation.
Love means never having to say, "Put down that meat cleaver!"