I think the term you are looking for is "comorbidity." There is research showing that BPD commonly has comorbidities with multiple other disorders -- depression, anxiety, substance abuse, others. People are complex, and personality disorders manifest in very individual ways. We see a lot of common traits in the people described here, but expressed in very different behaviors and thoughts. Make sense?
The high-functioning and low-functioning terms aren't really part of a clinical diagnosis. They can serve as a shorthand to describe how a pwBPD is presenting to the world.
So, the blaming and projection you saw, as well as the dwelling on negativity, are characteristic of BPD ... .but your partner has his own ways of manifesting them. You're asking if things will ever be forgiven? Well, one of the traits of BPD is the rapid cycling between emotional extremes. Your partner will probably -- when in a more positive mood -- forgive/forget any slights. But the disorder means that when he cycles back to a negative mood, he can go right back to ruminating on them.
As for how well people with BPD function -- yes, that varies quite a bit, just as it does for the rest of the population. It's also not necessarily stable. Someone with BPD can be high-functioning at some point in their life and low-functioning at others. I would guess that's dependent on other factors -- life stressors, depression, hormones, etc.
Totally agree with this. My husband was a high functioning BPD who held down a managerial position for 13 years.
Then he had a back issue, had to have surgery, couldn't work, met me , never disclosed any of his issues, things were bad right from the start for us, he got addicted to his pain meds, we had to move, he tried to kill himself, his dad died, and only in the last year has he kicked his habit, got into therapy , feeling stable and talking about going back to work... .he has been out of work for 7 years.
His mother refuses to believe any of this of her son as she has only ever seen him as a high functioning BPD and so a lot of these things were not happening.