Good job on standing up for yourself! I remember how, after a while, I would be hesitant to speak up, as it was often easier to let things slide than to deal with my ex's rages. I guess that's part of how they break us down
I was trying to do NC, which became LC because she got so m ad when I told her I couldn't talk to her anymore.
If I read this right, it sounds like you set a boundary, she had a tantrum, and then you weakened your boundary in response to her tantrum. What kind of precedent do you think you have set here, and how might that play out in the future? IMO, if you set a hard boundary of NC, your BPD ex will probably want to break it down. It's up to you to enforce that boundary. If you're truly done with this r/s, go full NC to create space for healing and moving forward.