lovevlm 
Welcome.
I'm glad you've found this site. It helped me a lot in dealing with my ex. Difficult family members as well.
My question for you all is how did you make the transition from learning that your parent has BPD to accepting and actually putting measures in place to create a sustainable future?
So you already know the parent has BPD. I think from there you can decide on what your "sustainable future" looks like—so think about what relationship you want with your parent.
For example, some people want detachment and a clear delineation of where the BP parent begins and where they end. They want things like not being coerced into caretaking the person with the PD. They want things like being empowered to choose if they want to take care of the pwBPD and to what extent. If that's what they want, then the measures you speak of would be dialogue tools.
Lawson suggests (I've used this):
1. "I am..."
2. "I will..."
3. "I won't..."
Putting this measure in place means that you go in ready with this dialogue when you discuss things with your parent. Personally, it means sticking it out even though it may feel very frustrating to implement. In my situations, I think the rewards have been well worth it. It stopped me being manipulated, it kept people from coercing me into doing things, it prevented me from taking on guilt that wasn't mine, it helped me feel and remember that I did
much better than I would in all those situations, I felt prouder of my actions, etc.—all of which are benefits whereby we're in the same boat of what we generally want in these situations. So I highly encourage you continue understanding and deciding which tools you want to use.
Also, in times of deep hardship, what helps you all stay grounded, calm, cool, and collected? (I've tried telling myself "separate her from the illness", "this is not her fault and not her", "her intentions are not bad" and "breathe")
What helps me return to feeling grounded, and calm, cool, collected would probably be getting into "wisemind" states. You can find out more about it
here. I've found the easiest way to do this is using self-validation techniques (found elsewhere on this board). It will get easier the more you practice on your own and while you're in days where you've got to deal with the person for whatever reason.
I think you're on the right path. I'm interested in what others have to say to your other experiences. The outline for improving your life with a BPD parent is
here.
Personally I really enjoyed
this book too, even though it's a children's book.
If you have the $, then I highly recommend you get a qualified T. That's what I'd do if I had a to-do over again.
Good luck and enjoy your improving peace. I hope you'll share more.