I am in a very similar place to you... . or where you were. I was under the misconception that if I explained the logically and we focused on the facts... . that it would all become clear.
After last storm out on marriage counseling I finally had a trained person point me in the right direction. And yes... I realize that I was part of the problem because I was arguing with an unreasonable person. So... I am attempting to cut out my part of the conflict.
Anyway... . maybe I will rephrase the question some. This is our 5th round of marriage counseling. This will be the 3rd round with a trained counselor. The first couple rounds were with pastors that cared but... . in my estimation... . didn't have the knowledge or skills to deal with this. In fact they found some of the stories I was telling so fantastic... . that there was natural skepticism.
So... storm out at last counselor and said she would never go back to that one because she was "on my side". Practically speaking that meant that the counselor enforced rules in the counseling office. No interrupting, don't claim things and then say you didn't say it... . etc etc.
Now we have been to one joint session (the start) and both have had individual sessions. Next week will be our next joint session and start weekly joint sessions after that.
With previous counselors wife has agreed to go for formal individual evaluation/diagnosis and then backs out because "i control the counselors and psychiatrists"... . because I will use the information to take the kids and toss her out... . that the counselors don't know what they are doing... . etc etc. That she only agreed to go to make me feel better about going.
So... on the one hand counseling is a place where we can attempt to communicate with a referee. That is better than nothing.
But on the other hand... . I don't want to participate (for too long) in a process that is a farce where 1 person is trying to follow the rules and the other person is trying to evade rules and heap blame on me and avoid accountability.
How do I go about figuring out how long to participate?
I'm no expert and I don't know what is going on with you and your wife... . but... . put yourself in her shoes for one moment.
Although a lot of us here have gone through a lot of things with pwBPD or just pwPD... . diagnosed even - there is no way for any of us to diagnose someone, even based on their behaviors or symptoms.
So you want to take your spouse into session and bombard her with "you have a mental illness" - and you think this can help your marital situation... . how?
I'm not suggesting she is or isn't. And I surely am not trying to take away from the pain and confusion you must be going through. But if I were in that same boat and my spouse takes me into a session with a therapist and I get ganged up that I have a mental illness... . it's like an intervention finger pointing blame game instead of "couples counceling".
I know when I went to sessions with my wife, I was really wanting to be there when she "got it". When a lightbulb went off in her head and she could finally get on the same page as me and we could fix whatever the mess was that was going on.
But that never happened... . well... . I was there when the lightbulb went off and something was "got" - but it was me who finally understood it. It was me that understood what I was dealing with and a lot of the issues were mine as I was so wrapped up in trying to fix her... . I missed the bigger part of the puzzle to see what my deal was (if this situation is so wrong, why do I put up with it, and all that jazz).
I don't have any suggestions on how to do what you are asking. I'm sorry. I wish I did.
But you are at the right place. And you are not alone.