Welcome, Jerapais! I am glad you have not given up on trying to find answers. I am so glad to hear you are also now in therapy. This is sometimes the first step to opening your eyes.
pwBPD do not "present for interpretation," meaning they don't often go to therapy because they think nothing is wrong. Often they think the problem is the nonBPD spouse.
BPD is also a spectral disorder. That means symptoms can be mild or incapacitating. One does not need the full-blown diagnostic criteria to be BPD. The same for many personality disorders. Some BPDs are severe and in and out of institutions. Some are very high functioning and hold high-level jobs.
Sometimes there is a life event that makes them start searching. The death of a child or sibling, the loss of a job, the death of a parent, etc. Usually they are aware on some level that "something is wrong" but are frankly too terrified with finding out what it is. For instance, my uBPD/uNPD H lost his mother to a long illness who was the codependent in her marriage. It was a huge blow to him as his father, uNPD, is the survivor. uBPD H was grieving and angry and projected this onto me with demands and rages. I suspect H was emotionally abused by his uNPD father from what I have observed in family interactions. I also suspect his children might be BPD or NPD, and his x W might be BPD.
I have been using some communication techniques I have found here and it has help with H volatile rages at me. I have been able to diffuse many episodes of rage.
It's common for those raised by BPD or NPD parents to find spouses who are BPD or NPD. You are not alone. It's called a repetition compulsion and it's not your fault. Often those of us become enablers or codependents without knowing why.
I have found, however, that most of the work in the marriage must come from the nonBPD partner. Usually pwBPD don't have the perception of their behavior to see something is wrong and how to deal with it.
It is good, though, you are here to find answers. Most of us are well aware of the pain and confusing of having an abusive and volatile spouse.
If you have not already done so, please watch this film. I wish you the best. Please join the conversations.
https://bpdfamily.com/content/Dr-Jekyll-and-Mr-Hyde