hey problemsolver
ive enjoyed your questions. they make for good discussion and its useful to try and understand the dynamics of the relationships weve been in. what i dont see in this particular set of questions is much personal responsibility, that is, where we, or i, or you played a role. thats useful too, and im going to answer in that spirit.
1) examine your question on its face. "is it normal to be put in a 1 way relationship?". successful relationships of any kind are not one way. so what kept you in a situation you were uncomfortable with? it sounds like it conflicted with your values. does what you described fit under general BPD behavior? no. people do have varying opinions about open relationships. i dont judge, but i do know that its not for me, and i would not be comfortable in a situation where my partner was pursuing such a thing.
2) in my relationship there was no devaluation stage. in general, i would be devalued when she raged. call it black and white thinking, dysregulation, any number of things. i think that this question assumes we all virtually experienced the same relationship, and stages, and we did not. i put up with the abuse for many different reasons, some make more sense than others. one reason is that it was not in stages or permanent, it was intermittent. if it had been constant, or even more consistent, i likely would have left... .many of us (not all) would have. in some cases there are certainly clearer "stages", and the reasons may vary. some express prolonged hope of returning to the idealization stage. thats usually intermittent too. no one deserves abuse or devaluation. the question is, if you put up with abuse, why?
3) terms like "emotional vampire" are probably not the most accurate way to describe our exes. my ex had positive qualities or else i would not have stayed. keep in mind too, that vampires have to be invited in

4) im four and a half years out. time gives you a lot of perspective.
5) i personally wouldnt use the words "feel sorry for", but thats semantics. i feel compassion for my ex, as i do for all of the mentally ill. i feel tremendous compassion, i always will. i dont feel pity, shes an adult, living her life, making her choices. but i know what her family dynamic was like; i know that she was frequently rejected by her father and it breaks my heart. i know that she did not ask to have a personality disorder. i know that finding happiness with life or within herself, finding a stable, happy, healthy romantic relationship, are very very difficult for her, and that breaks my heart too.
6) there is some more overgeneralizing here. can you clarify what you mean by sabotage? how do you think your ex sabotaged the relationship?
7) not on the surface. i wonder if you might be asking if you felt compared to her exes and in a competition? id gone through that in previous relationships. my ex did mention her ex with indirect comparisons and i expressed very quickly that i was totally uncomfortable with that. in fairness i did it too, and she wasnt comfortable with it either. we stopped. its best to resolve past relationships before entering a new one. there were forms of triangulation. particularly, the way she would try to pit me against my mother. that should have been a deal breaker and i regret that it wasnt. triangulation is not a BPD behavior, it is something that everyone does, and there is such thing as healthy triangulation. more importantly, its something we can be conscious of; we are not forced into triangles. we can get off.
8) frankly, abandoning groups of friends or careers is a personal decision, not someone else ruining our life. thats enmeshment and poor boundaries, and thats on us entirely. i do know that my ex was very jealous of females; i had a group of female friends that had fallen by the wayside before her, that i wanted to rekindle. i found various ways to rationalize not rekindling them without blaming my ex, but thats really all it was, and its on me.
hope this helps
