Hi there,
I'm so sorry for what you are going through. So much of it sounds familiar, though with me I'm the male and the BPD person was my wife (we divorced a few years ago). I don't envy your position. So difficult. The one thing that tipped me off to where you are at with all of this is the statement below:
He's convinced I'm narcissistic and has painted the picture for everyone in his life that I'M the problem. I go through periods of feeling crazy and wondering if it really is me. My heart hurts for him and what he's going through. I'm especially concerned about him receiving the diagnosis because he has worked in the self-help world as an emotional growth seminar facilitator and teaching parenting classes. He knows people with BPD and I wouldn't say he has a very good view of what that means. He's already convinced he's broken and I'm worried the official diagnosis will just push him over the edge.
You talk about how he blame-shifts it all onto you and makes it look like your fault to others (something mine did to me, too). You talk about feeling crazy and wondering if it is really you (same thing I went through). Yet you immediately jump to how badly you feel for *him*. There's a bit of a gap here, don't you think? Where are you allowed to feel anything for yourself? From experience (and from reading all the similar experiences in this group), one of the big problems people face who have been in a close relationship with a person with BPD is that they divest themselves of any right to their own feelings. We almost feel bad, like we are doing something wrong, if we aren't totally focused on them (and of course, if we aren't totally focused on them, we're being "selfish" and "narcissistic", right?). We are totally wrapped up in them, to the point where we lose ourselves. For me, this was something that was burnt into me by years of trying to cope with (and survive!) my BPD ex. With each crisis, with each accusation, with each tantrum, with each time they blame you, with each time they are unhappy with you, with each time they turn it around on you, with each time they take and take some more, I lost myself one bit more... .lost myself into ruminating and trying to figure it all out, and lost myself into focusing MORE on their feelings and LESS upon who I am and what I feel. We may be dispositionally prone to this, but it is still an effect of living in a close relationship with a person like this. We become automatons that exist to revolve around them. So, please, please, please give yourself the adequate head-space to feel some pain, grief, or maybe even anger for yourself because of what you are patiently enduring.