I'm so sorry for what you are going through Milly. There are some great lessons on the right side of the page that can help you navigate through your relationship. You'll find techniques to help communicate better, how to set boundaries, and how to take care of yourself. You can't change your pwBPD but you can change how you respond to him.
You mentioend that you believe your pwBPD cannot make it in life without you and that you feel the same financially toward him. Distinguishing between helping someone and enabling them is important not only to your well being but to his also. Here is an article on enabling vs. supporting:
https://bpdfamily.com/message_board/index.php?topic=95263.0