Hope for the best. Plan for the worst. If you've not done so, consider reading Splitting by Bill Eddy and Randi Kreger (
https://www.amazon.com/Splitting-Protecting-Borderline-Narcissistic-Personality/dp/1608820254) It will hep you plan for what you may encounter should you (or she) choose to separate and divorce.
Are there any other threats besides divorce? Any chance at DV? Have you considered documenting the divorce threats and perform some trend analysis? ie, it is getting worse?
Sounds like a difficult situation. Find time for yourself out of the emotional pressure cooker and enjoy life for a few precious moments. Eat well, exercise, get good sleep. Good Luck. CoMo