Longer term you will hopefully feel better again, and come to a sense of peace with this relationship.
For whatever it's worth, I think people with HPD are mostly reacting to their damaged self-esteem. It's not necessarily done to cause others any harm (though it does hurt), but because they fundamentally don't feel good about themselves, so attention/validation from others provides a temporary bit of relief.
On the flip side I learned my own sense of self-esteem was on shakier ground then I believed, so I suppose as a result of that, and a lot of introspection, my self-esteem has overall improved. Not because I think of myself as having great self-esteem, but because I'm more aware of how easily toppled my sense of self is. I also have learned a few other things as well.
One big difference though is you wrote about how attractive he is. The woman I met has made some changes to her personality, and still wants a relationship, so I didn't ever experience complete devaluation. She is about my age though, and while attractive in my eyes, it wasn't entirely about that because she isn't as young as she once was. He might change, or at least outgrow some of the symptoms, but if attention comes easily due to his appearance, realistically he is probably not at a point where he is ready to start the introspective process. Sorry

Please feel free to write as much as you need. I know how badly it hurts to love someone, and to be so easily devalued for new attention.