While the perceptions and behaviors of a person with acting-out BPD traits (pwBPD) are mostly self-centered, they are also often controlling and dictatorial. For example, you would like to find helpful counseling for yourself and the children. She may oppose it but as my lawyer stated, Courts love counseling. In a dispute between counseling or not counseling, family courts generally enable the parent wanting counseling.
It's not surprising that disordered parents want to pick easily swayed or biased counselors. If this is your situation, strategy may be needed. If you research and determine which are the more experienced and more perceptive professionals that accept your insurance, then at the right time you can present the vetted list to the court and propose your spouse select from among those. Courts like to have input from both parties and will like that. This may avoid your ex managing to pick ones ex can control/influence.
Your stbEx probably resists therapy for herself - denial, blaming and blame shifting onto others. You have found you can't lead her there. And you will find that divorce/family court won't even try. All the professionals will more or less deal with her as she is. You are wise to do the same. Focus and prioritize on (1) yourself and (2) the welfare of the children. As much as we didn't want to take that path, divorce enables us to reclaim our authority as a parent.
Living in a calm and stable home, even if only for part of their lives, will give the children a better example of normalcy for their own future relationships. Nearly 30 years ago the book Solomon's Children - Exploding the Myths of Divorce had an interesting observation on page 195 by one participant, As the saying goes, "I'd rather come from a broken home than live in one."
Ponder that. Taking action will enable your lives, or at least a part of your lives, to be spent be in a calm, stable environment — your home, wherever that is — away from the blaming, emotional distortions, pressuring demands and manipulations, unpredictable ever-looming rages and outright chaos.
An excellent guide to assist you through the legal quagmire of a divorce is William Eddy's excellent handbook "
Splitting: Protecting Yourself While Divorcing Someone with Borderline or Narcissistic Personality Disorder". It is a great complement to the local resources such as counselors and family law attorneys, not to mention the peer support here.