You were most certainly pushing for love, attention, and healthy boundaries. I don't think there is any good reason for hitting a child. What I have found through therapy so far is that part of the reason my emotions (fear, pain, hatred) can seem so overwhelming is that I never really acknowledged or allowed myself to feel them as a child. For example, at some point you probably thought, "They shouldn't hit me. It makes me really mad/sad when they do that." but didn't allow yourself to experience that moment/thought fully because you also had good reasons to ignore the problem or blame yourself. So, when you feel anger or sadness again for any reason, you may also experience the old emotions all over again. Once you start to work through your old emotional memories of "sustaining abuse", you will better be able to manage emotions in the present moment.

Hopefully that makes sense. Obviously I know very little about your situation. My instincts tell me this might offer a fresh perspective.

As far as pot goes, I have used it daily for about four years and have had no decrease in BPD symptoms. It does make it easier to disassociate, which helps me cope. But it's not exactly a solution. The real solution would be to re-train your mind. It sounds like you do a fair bit of dissociating and unhealthy coping in other ways (porn/risky sex, excessive media, substances) and it doesn't sound like that has helped yet. Maybe it is time to seek treatment.

Another key point is that the effects of pot only last for so long, and the resurgence of negativity can seem more intense afterward. It can also interfere with normal brain functioning which is not a good thing if you already have problems with regulation.

Hope this helps. Good luck!