Hi Veteran,
Welcome to the BPD Family
I know this sounds flippant but it really isn't it is about safety... .Remove any guns from the house before you have this type of discussion with your wife.
Suicide Threats. My significant other (SO) had this happen during his marriage to his undiagnosed BPD ex-wife (uBPDxw). He would call 911. He is not a professional, not equipped to deal with this type of situation, are the threats real or drama? So he called in the professionals. Get the police there to assess the situation and de-escalate things, get her to the Emergency Room for evaluation, and get doctors involved. I would suggest doing the same if your wife makes suicide threats.
I would also do a consultation with an attorney and find out about your rights and how divorce could effect you financially. I assume child custody isn't an issue. I would do this also before having any kind of discussion with your wife, and I would do this without her knowledge.
There is also a book I'd like to suggest... .
Splitting: Protecting Yourself While Divorcing Someone with Borderline or Narcissistic Personality Disorder by Bill Eddy, Randi Kreger
Make the most educated decision you can, have a plan in place, and then approach your wife.
Take Care,
Panda39