Hi CanadianDaughter,
Thank you for sharing some of your story with us. I'm sorry that your relationship with your dad is so difficult, especially now. That is nearly your whole childhood that was affected by his instability and mood swings. It is so hard on a child who only wants to be loved.
So today my father is back to his old ways and our relationship is hanging on by a thread.
This is so much what we see in a pwBPD. The unstableness is very difficult for us, yet so normal for them. I suppose it is also normal for us in a sense that we don't know much of any other way with them. My mom was an uBPD, and to this day I still have trouble with moody behaviors in people. That's part of why I am on this board, so that I can learn to heal and cope with the unhealthy things I learned in my childhood from my uBPDm.
What have you read so far to help you with understanding BPD? I am going to post a link for you of a book written by a woman who's mom was uBPD. She writes from our perspective, of what it was like to grow up in such a home, and how it has affected her life. She doesn't leave you hanging though and shows how she has been able to unpack her past and bring it into the present and thus become much healthier.
https://bpdfamily.com/message_board/index.php?topic=298995.0 I can tell that you are a great D who really loves her dad and wants to share life with him.

Good for you! Don't give up, but work on healing yourself and that will improve your view of yourself and allow you to relate to your dad in a healthier manner. Have you ever considered starting T with someone who understands BPD?
Wools