Hello Nanabee and

You're not alone in being married many years to a spouse with BPD traits, and then having things really escalate after an intense emotional situation. I'm so sorry this is hitting you and your family now

As you look back on the past, what were the less-extreme signs of BPD that he may have shown?
Also, do the two of you have any children? If so, are any of them living at home?
One of the hardest yet most freeing lessons we can learn here is that we can't control anyone else's thoughts, behaviors, words, or actions. The only person in the world we have control over is ourselves. So, it may be more helpful, long term, to focus less on "how can I guide him out of his splitting?" and more on "how can I improve my mental health and take care of myself, no matter what he's doing?" Counterintuitive, especially as you love your H and wish you could help him, yet the best way to introduce positive changes into a relationship is through working on and changing yourself.
Have either of you been in counseling or therapy? Even if your H doesn't agree to go with you, or won't go on his own, you can still get individual therapy for yourself, which can be a great way to find areas to make changes in the relationship dynamic -- all on your own, without needing him to cooperate.
Take your time, settle in here, check out some of our workshops (we have one on
Splitting if you haven't seen it yet) and articles (like this section on
When a partner/spouse has Borderline Personality Disorder).
Let us know your thoughts -- we'll be here;
kells76