I would appreciate any words of advice from those who have gone through a divorce with a BPDx after a long term relationship.
Hey Awakened and welcome to the family. I'm really sorry you're going through this because I know first-hand how much it stinks. My marriage was 23 years and like you, I discovered my wife was unfaithful...or at least preparing to be unfaithful. When that happened, everything changed and things became ultra hostile out of nowhere. I was clueless what was going on.
The most critical advice I can give you is pointing out that this will be a process going forward, not a singular event. Will you leave or will she? Is counseling even a possibility? What are your state laws on divorce....is there a waiting period during separation? Think about the bare basics for now and try your best not to tackle the big picture.
One thing I'll say that most would disagree with- regardless of what happens, this process is a billion percent smoother if you and your wife can openly communicate. Even if it's 100% over, you'll still co-parent for life and the legal process can get extremely ugly. The more you can find common ground to communicate on today, the better it will serve you long term. Don't burn bridges, not yet anyway, and get legal advice as soon as possible. They'll help you game plan.
Finally, don't forget about yourself in this process, as silly as that sounds. Your emotional needs matter and counseling wouldn't be a bad idea. We've all been there and it helps. Also lean on friends and family; they won't get it sometimes but that's okay. You need support and you'll need to fill the void as this process moves forward. Start thinking about that now.
Just let us know if there's anything more specific we can answer for you.