I think my friend has borderline - don't know what to do

I've been friends with someone who is now around 17 for about 4 years now, though I've never met him in person - stictly online. He talks to me sort of like someone would talk to a diary, and I've always been an empathic person, so I listen. But as I learn more about psychological disorders, I start to realize that his relationship problems with a certain friend of his doesn't really have anything to do with his friend, and everything to do with him. I thought for a while that he was clinically depressed because he had very low levels of self-worth, was generally depressed, irritable, and thought he was a bad person. I've lately been taking other habits of his into account though - not only the behaviors he displays towards me, but also how he says he feels about other people.

- He fears abandonment, particularly from his friend
- He will sometimes get way more angry than any situation warrants
- He sometimes sleeps for 14 hours and then other nights doesn't sleep at all
- He engages in substance abuse
- He sometimes will take pleasure in making other people angry and feels compelled to hurt others, but then later apologizes and says that he really wants to stay friends (this is mainly his behavior towards me - I've made up my mind many times not to talk to him, but my empathy brings me back)
- He pulls people toward him and then pushes them away - his other friend is always either angry with or in love with him
- He gets bored and lonely easily, and thinks he is a bad person and low self-worth, has little empathy for other people
- He sometimes has mild paranoid delusions that everyone is against him
- He frequently threatens suicide

The problem is, I've tried to get him for years to see a qualified psychiatrist, with absolutely no luck. He refuses to believe that anyone can help him. The closest I've ever gotten was when he said if I specifically ever become a psychiatrist, he'd see me, but that was it.

I'm so frustrated because he won't stop doing weed, and he won't see a psychiatrist. He thinks that he chose to be in this kind of pain by choosing to be a terrible person, and being in a relationship with the person he's liked for the past 5 years will fix his life.

What can I do? Are there ANY suggestions someone can give me? I've given up trying to convince him to see someone, but is there anything I could say that a professional might say, besides being empathetic, that would get him to see that he's not a bad person and being in a relationship has nothing to do with his pain?

Keep in mind that some of that may be basic teenage problems. Psychologists often refrain from diagnosing BPD in teenagers because we tend to be a little emotionally unstable anyways

Id encourage him to go to a psychologist thought, its really the best option.

He won't go to a psychologist... I've been trying to convince him for years.

This seems unusually unstable to me - he's miserable, wants to die, and can't form normal relationships. I don't know, maybe I'm just hypersensitive.

Would he consider seeing a therapist informally? Like just meeting with one for lunch and talking with you there?