Hi clp82, welcome to the boards

You're in good company with so many others who are struggling to problem-solve with a spouse with BPD.
Sounds like you are realizing that living together with your BPDh is a nonstarter as long as he stays at the level of functionality and behavior that he's at.
You're floating the idea of a separation, and I notice you haven't mentioned divorce. Is divorce on the table for you, do you think? Or are there some reasons you're thinking just separation?
What would your hopes and goals be, if he did end up moving out and you were separated? Would getting back together be an option at all? If so, what do you think it'd take (on your end, on his end)?
That's frustrating yet not surprising that he didn't follow through with setting up couples therapy. Sometimes couples T's can assist in a separation. If that's a big goal for you right now, I wonder if it'd be worth it for you to just set up the appointment (even if he "should have") -- to get the ball rolling with seeing a professional and maybe getting a professional to assist with the structure of the separation.
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This stood out to me:
Been walking on eggshells for years as his favorite person but also having to be the person who gets him off the suicidal edge all of the time. It's exhausting!
I can imagine the total exhaustion coming from feeling like you have to talk him down.
What approach do you usually try?
Have you ever tried anything different? Do you think you'd be open to trying something new?
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Fill us in whenever works for you;
kells76