Hi Lollypops
I just ran into this book on another forum, one where BPD sufferers sometimes go, and it was recommended as a good starting point:
Borderline Personality Disorder: A Guide for the Newly Diagnosed
https://www.goodreads.com/book/show/13436423-borderline-personality-disorderI haven't read it myself yet - would love to know if its helpful, and how it goes with your son. This sounds like a critical period that needs focus, and how much love you have had for him to support him over all these years!
One quick note - even though the illness is associated with strong emotions including rage, it doesn't mean those emotions are fake or have no reason at all. They are dysregulated, not under control, last longer and are stronger than normal, but it doesn't mean they aren't real. Myself, I think the lack of control somehow is related to a lack of trust, but that is just my thought.