My (20F) friend (19M) recently started drinking and has gotten meaner. How can I approach this gently?

I am really concerned about my friend's drinking as of late. He didn't really consume alcohol (aside from the occasional function) until a few weeks ago when he got back from a short break where he had been allowed to drink. Then, he started talking about it nonstop and making plans around when we could drink together, and his attitude towards it became super worrying. I told him that I was getting worried about him and he got mad at me and basically said that because I have my own issues with alcohol, I couldn't tell him what he could and could not do, and because he wasn't drinking all the time, it wasn't an issue.

Well. He started drinking all the time. Like, nightly. I think for some reason, he's weirdly proud about it, but he can't even get it by himself, and to be honest, I'm worried about what's going to happen when he runs out. Since then, it's like he's constantly a jerk to our mutual friend and me, though it's more aimed at me. He's not outwardly an ass, but he'll say things or throw in a comment that he wouldn't have said before he started drinking. He refuses to listen to anything I have to say on this topic, which is why I'm looking for help.

I'm scared of him and his attitude. It's just little things that I've noticed, except for one instance that really stood out to me. He knows I hate silence. He knows that I hate being ignored. Sometimes, when I say something, I just won't get a response, and he knows how triggering it is for me. He knows so well, that when I called him out and was like, "Can you please say something?" he cut me off before I could finish what I had to say, and he said, "Yeah, we know. Your dad gave you the silent treatment, and now you have BPD."

I don't think I deserved that. That's the worst thing he's said, but it's so hard to hang out with him now. Our personalities have started to clash, and I can't figure out how to help him because I know it's because he started binge drinking. Not to mention, he's extremely selfish and I'm getting sick of it. I want to stay friends with him but I can't spend every moment worried that I'm going to say something to piss him off or that he isn't going to insult my mental illness. And I don't want to lose our mutual friend because they're kind of all I have right now. My frustration is building up and I'm afraid I'm taking it out on him (not that he would notice). How do I bring anything up without setting him off?