Don't be so hard on yourself for going through multiple repeats - many (dare i say the majority) of the posters here on the leaving board have done the same.
You've certainly wrote lots, but it sounds like you have great insight into your situation and into what YOU want:
I still feel like my life is not my own and this is unnerving.
This really stood out for me, what would it mean for you to own up to your own life?
You understand that no one should be responsible for another person's emotional well-being or happiness.
What really helped me move on was realizing a few things along the healing path, here are a few off the top of my head:
1. FOG (Fear, obligation, and guilt) are extremely powerful, but at the end of the day, it's up to us on how to react to it
2. It's important to judge the actions of the BPD. That is the reality of who they are and this is unlikely to change
3. No one can help them besides themselves
4. Understanding my role - that as toxic as this relationship was, it took 2 to tango. Unlike someone with BPD, we have are equipped with more emotional stability that allows us to work on our own issues
there are more that i'll add as I recall them. I know these sound unfeasible, but trust me... I am also 3 months out and once you're emotionally detached, you wil be free to work on you.