Well, you have read the countless stories... . Did you find hope in reading them? Are there any true happy endings? I haven't found one.
I don't remember where, but I found online a piece of information about how BPD to some degree might be hormone connected (i haven't verified this info) and that there are potentially progressive medication therapies on their way but I wouldn't bet on it. I don't know, there was info about how pwBPD (women particularly) had almost perfect (meaning without this nonsense) behavior while being on hormonal birth control. Also I can't provide any references but I have stumbled upon such info while researching BPD online.
I also would give everything if there was a permanent cure for this and if there was a possibility to get back my gf but there is no quick fix, meaning that you will have to sacrifice something - your time, identity traits, patience with no guarantee of success.
In my quite short journey towards leaving I reached a phase where I would fantasize how relieving it would be if my gf crashed in a car accident and died. Oh it would solve a lot of problems for me. These were very brief moments but they kept emerging with certain regularity. Tho I would immediately punish myself of thinking such things - no I am a bad person, who wishes death for someone, especially when they love them?. But that was a fact and it got me thinking - something is seriously wrong and I should get out, that is not true love, that is something else. So yep - these thoughts were a good control-mechanism for me to know when it is time to leave.
Nevertheless I am so mixed up in my feelings - I miss her, I wish she was beside me, I want to know what she is doing, and everybody goes thru these stages. Eventually it gets better, so I have read

Also happiness doesn't come from outside, it comes form inside, from our choices. If we feel unhappy then it is probably because we have made poor choices. And to change that we have to change our choices.
Best of luck of finding your path towards your happiness.