I'm finding it hard to deal with friends depression

Hey, A good friend of mine who I live with is really struggling with mental health stuff. Let's call him D. Low self esteem and loneliness are the two really big things that are getting to him. I try to be supportive but recently it's getting difficult. I've got bipolar so I'm trying real hard to be strong for him. He drinks all the time and isn't a great drunk, texts me a lot about being suicidal. 4 times now I've had to call ambulances for a failed overdose or police to go find him when he tells me he going to jump off a bridge. A recent thing has tipped him. D went on a couple of dates with this girl, another friend of mine "s". I introduced them. My other friend " n" fell for her though, and she fell for him, so told D that she wasn't interested. N and S have been together for a while now and are moving in together. D is freaking out man, I don't know what to do. He's like banning the girl from the flat, talking about how he wants to be dead and no one will ever love him, and how he's mad that I'm friends with them. He's getting therapy pretty soon I think, but in the mean time I don't know how to help him. All this stuff has triggered some pretty mean lows for me. My boyfriend says I should leave it, for my own health, but I don't feel like I can because of his suicidal tendencies. I don't know. Ideas?

So, which one is your problem?