When am I safe?

Hello. I'm new here and I have a long distance partner who's diagnosed with BPD. I'm hoping there's hope for us to last, but everything I've read basically seems to imply it's impossible. We've been together for a year. There's constant improvement in our communication and bond, but he struggles a lot. He hurts me (never physically, but he becomes extremely hurtful with his words when he's stressed) and I try to be patient, but I'm scared. What if I'm just his "FP"? How long do those obsessions last? Is a year long enough to know? I've worried for a long time that he really doesn't love me as much as he thinks and is just one mental mishap away from throwing me away. He wants to get better and is constantly working on himself. He's made so much progress, even just in this last year. So is it possible for him to stay in love with me? Or is it impossible for BPD people to do that? Is there any hope or point in continuing to be patient while he learns to cope? Or am I inevitably going to be "discarded" like everyone else here seems to have been?