Loboe99, welcome!
You will start to have some answers here in the forums.
I am so sorry you are having to go through this, but you will get some clarity now you have started to research BPD.
It's is enlightening to see the "lightbulb" go on and you see it's all starting to add up and finally make sense.
The confusion lifts, but it's still frustrating nonetheless. It's good you see a pattern in his behavior, and a clinical picture starts to emerge.
Read the article here on FOG: fear, obligation and guilt.
This will be a start. In a BPD family, all seems to revolve around the pwBPD, so protect your son.
https://bpdfamily.com/content/emotional-blackmail-fear-obligation-and-guilt-fog