Hey friend, I'm so sorry you're going through this. Much of your story resonated with me and I feel your pain. It does get better with time though and the secret is focusing on yourself for a bit and working on your own mental health. It sounds like you're already off to a great start.
1) What would you do in my situation for the breakup? I know I have to end this relationship even though a ton of me still wants to keep trying especially because she is acting so sweet now. I think I wait until I get set up in my new apartment.
I know this is in the "detaching" thread so most of people's answers will focus on you moving on, creating space to heal, etc. Yet your question here is an outlier- why do you know you have to end this relationship? I get why you're torn, I'm in the exact same situation. I also get why you'd be scared of her. It sounds like you still have mixed feelings though and you need to work through that on your own. Nobody here can help you make that final decision.
With that said, you probably know that she's acting sweet because BPD goes through cycles (see the categories at the top of this page for more guidance). Right now, she's back in the love bombing stage to fight for your affection. That might last a day, a week, a month, a year...who knows? All I can tell you is that now is the ideal time to start putting up healthy boundaries while moving into your own place. That somewhat breaks the push/pull relationship.
2) Tell me about these withdrawal symptoms and how to cope with them. They are awful. How long do they last? What do I do to allay them? I am like willing to check into a detox facility if I need to.
I'm not going to try to sugarcoat this- you're going through genuine trauma right now and your world probably seems upside down. I've been there...everyone here has. It really really stinks, but you're going through a grieving process and it's going to take some time. It is different for everyone, and there's no set timetable for healing. It starts with you though and focusing on your own needs, your own passions in life.
My advice, think about your life pre-relationship and remember what you used to love doing. Then do a lot of that. Find yourself again, pick up new hobbies, spend time with friends/family, and stay in counseling...talk this stuff out! I'm no expert, but it feels like the turning point for a lot of people here is when they realize that this isn't their fault. We could swap places in the relationship, and it would still reach this exact moment sooner or later because of BPD.
So hear my words- this is NOT YOUR FAULT! It really isn't. She's mentally unstable and she's not trying to hurt you, but her entire world runs off of emotions in the moment. It's not exactly her fault either though because until she wants help and takes counseling seriously, these patterns and cycles will continue.
3) The meaning of the relationship. No normal person would be as cruel to a partner that was as good to them as I was in this relationship. It feels like none of this means the same thing to her as it did to me and our "love" for her means something very different than what it does to me. Like she "loves" the hell out of me right now because I'm basically ignoring her... That isn't love to me... How did you create the story and meaning of your former relationship with the pwBPD? It feels to me like I had a relationship with an alien who just didn't feel the same things as I did? I know she loved me but her biology is just so different from mine. This is the most confusing part to me.
I covered this in my last answer- my ex was a loving, caring, compassionate woman with a severe mental illness that dysregulates her moods. Sure, I hated her for awhile but eventually I accepted that she's suffering more than I am and this rollercoaster of emotions may never end for her. I honestly feel sorry for her, just like I feel sorry for your wife. They can work past this with therapy and time.
To answer more directly, she does love you. She probably hates you too, but not as much as she hates herself at times when the world just doesn't make any sense. That's just my viewpoint though and others will give you very different answers.
Good luck, my friend...I'm so sorry you're in this situation. Keep your head up, focus on you, and you will get through this one way or the other.