How do I remain friends with my boderline/narcissitic ex-boyfriend?

We broke up a year and a half ago FYI. My ex has been telling me that he's offended when I mess around with other people even though I never put out or was in a relationship. He has sex, and I don't care. When he gets in a relationship but says he loves me more, I get hurt. He seems to care only for himself. He got this girlfriend and accused me of being an asshole and freaking out on him when I just told him my feelings. We've been courting/dating/been exes for 2 years. He took my virginity. He doesn't show me that he cares. Everything is just so empty. He told me that we don't know what the future has in store for our romantic love, but we have not seen each other in 1 1/2 years and only wants to be with me on his time clock but would get mad if I had a relationship of my own. He asks me to promise me I will never leave him and has threatened suicide before and attempted it multiple times.I would love to fall back in love with him, but I feel like I have no romantic love to give him after all the hurt he's caused. I think people with BPD need unconditional love but need to know they are hurting people. How do I remain detached/still his friend?