Yes, I have have seen therapist personal for the past couple of years on an off, and not reluctant at all to more. I have not had a chance to see them as he was originally for our family and is reluctant to touch this.
One question I learned is okay to ask a lawyer, I would think the same goes for a counselor... "If you were personally facing a situation in your family matching mine, who would you turn to for representation/counseling?" Lawyers, counselors, etc know, or should know, that they may not be the right fit for every person walking in their door as client/patient. Does that perspective make sense? Surely your therapist could point you to someone more experienced in what you're facing, right?
As regards your other questions, here are some general responses, probably too brief to be specific.
Counseling is good. (1) Good for you. (2) Good especially for the kids, so they have additional resources to help them keep a good perspective. (3) Good for the spouse too, though with BPD behaviors/traits there is likely an intense Denial of culpability and a pattern of Blame Shifting. Hard to get meaningful therapy started and continuing long term with all that deep resistance.
Also, you did good to not mention your specific thoughts on personality disorders to your spouse. This is best left for a relatively emotionally-neutral expert to handle. Sorry, she wouldn't view you as emotionally neutral, not after 25 years of history together. Your life history with her made her resistant to listening past the huge emotional baggage of the relationship. BPD perceptions are more evident and persistent in close relationships, and what is closer than a marriage?
Sharing your thoughts with her family could be risky. Though some may be favorable to the reality of what you're dealing with, many will side with their blood relative, "blood is thicker than water". You should ponder any such actions very carefully, we are remote and can't advise you how that would turn out in your case.
After 25 years, your efforts to improve things met little success, as evidenced by your separation to regather your equilibrium. The fact is you can't 'fix' her. She has to want to change and success, if any, is usually with an emotionally neutral expert. Have your heard of the 5 stages of grieving a relationship loss? The first step is Acceptance... that it may not be recoverable. Sadly, it is what it is.
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