I don't know what else to do...

I hate asking this kind of thing, but I'm desperate, I don't know what else to do, where else to go, and I'm scared. I suppose I'm just going to lay all my cards out on the table for everyone to see so to speak. I feel that saying everything and being fully open is the most honest and effective way to show how genuinely desperate I am, and so, here it is~So I'm 15 years old, and nearly 16, and I'm bisexual. I realize this is young, but I've been through a lot, and had to grow up faster than most, and I suppose you could say that I'm not as naïve as would be expected at this age. My boyfriend is the same age, and is very similar to how I am in terms of his maturity and level of thought.To give you all some background, he didn't have the easiest time growing up. He has always been responsible for taking care of everyone's needs around the house, being the parental figure to his sister and essentially being the only one to raise her in a real sense, and overall, everything, and I mean EVERYTHING was on him. He got to a point where he was extremely depressed, suicidal, self harming, and got into some very bad circles via the internet. A few years ago, he came out and his mom kicked him out of his house saying that "she would not accept having a gay son".Naturally you'd think he would go to live with his dad then if nothing else, but that would've just been worse. He hates his dad passionately, and even I don't know much about him other than from what I've heard he's a scumbag. He hasn't spoken to him or had any interaction with him in nearly two years.Anyway, after he got kicked out, he went to live with his mother's friend and her family across the country. There he found refuge. He finally was in a good environment for him to grow in and repair himself. It's the place that he really sees as his home and his family, and it allowed him to be himself again. Like I said, it's where he's happy, at home, and feels loved.He's been there for a few years now and has only grown closer to the place and the people there, and over time, he and his mother have mended their old wounds to some extent and get along now. They talk on the phone often and that sort of thing.Recently, she got into an argument with him and threatened to make him come back. He is not a terribly emotional person, and it's very rare for him to cry, but when he told me that she'd threaten that, he was in tears. He was panicking from the idea of going back because of what it would do to him. Essentially he would be forced to leave everyone that he truly sees as family, his home, and everything else to go to leave in a place he loathes more than anything. The only other times he gets extremely emotional is when he talks about how much he hates it. Now luckily, he was able to talk his way out of that, and come to a compromise.The compromise is that he would spend most of the summer in Florida with her, but he would return as normal in August. I'll get back to that soon.For more clarity, I'll give a short summary of our relationship together. So he's a really great guy. He's honestly the best person I've ever met, and the way he is despite all he's been through is nothing short of a miracle. He and I have been together for quite awhile now, and we've got a very mutual understanding, and a healthy relationship. We're similar in all the best ways, yet different in area that compliment each other. For instance he's shorter than me and has a similar frame, as well as the fact that he's very submissive. I'm the opposite, and that's exactly what he's attracted to, which is certainly a plus. We have always gotten along very well even from the very first time we spoke to each other.Now, back to the Florida thing. He went back about two weeks ago. Very early into his trip I could tell he was acting strangely and something was wrong. He kept talking less and less, and seemed more numb every time. It got to the point where he started pushing people away left and right. He wouldn't open up to anyone, even myself. He's gotten extremely depressed, and refuses to talk to anyone for any substantial amount of time. He has begun drinking himself away. He's been completely shit faced for over half the time that he's been there, and no, before that he'd only had a drink twice ever if I recall correctly. He's been drinking because I guess he's decided that's the only little escape he has from there. He now goes into angry fits when we have talked where it's abundantly clear that he's not so much angry as he is just completely broken. I don't even know how to accurately describe it. He's not himself anymore, and each day that passes, more of him fades away.The last time he talked to me over the phone during his stay there was almost three days ago (as of the day of writing this at about 3pm CST June 3rd, 2017). I'd been trying to get ahold of him all day and finally late that night after I'd left 4 or so extremely worried-sounding voicemails, and a whole host of texts, he called me. He was drunk out of his mind which I think may be the only reason he actually called. He could barely make full sentences, was stumbling over his words, kept randomly laughing and then immediately seeming like he was going to burst out sobbing, couldn't focus on anything I was saying, and couldn't pay attention for more than a few seconds at a time. For him to even briefly listen to me and listen to my concerns, I had to start yelling to get his attention. I've never had to raise my voice at him once before then. Much later that night, he texted me before he went to bed and was very clearly even more depressed than usual, but had sobered up only slightly.Since then he's refused to talk over the phone or Skype, out of a mixture of shame, embarrassment, pain, and depression. He keeps going into depressed, incoherent, angry fits when I try to text him and he just keeps getting worse.He's completely broken, he's no longer himself but rather a hollow husk of a person, and each day that passes, more of him is fading away. I've tried almost every approach I could think of, and the most effective one (the face to face, in person approach) is one I can't do yet (because he's in Florida with his mom which is a fair crawl from where I live if that wasn't apparent already, and like I said, he'll be there until August). The closest time that I'll be able to see him in person and bring him away from there for a bit is in late July-early August.I've exhausted almost every other option and approach to helping him, but in a lot of ways he's stubborn. That hasn't necessarily ever been a bad thing, but it's a horrible combination with what's going on. He's gotten to the point where he won't listen to any kind of reason.I'm losing my David. I've tried almost everything to help and nothing has worked. At this point there's nearly nothing left of him. I don't know what to do. I'm scared that the little that's left of him will crumble soon. I'm not worried about whether our relationship survives, whether he can still stand to be around me after it, but I want so desperately for him to just be ok, and he's not. Far from it. If there's something I can do to help him I'll do it. Anything. Whether it makes me look bad in his eyes, causes me pain, or anything like that, I don't care. If there's anything I can do, I need advice. The feeling of helplessness when watching this happen to someone you love more than anything is indescribable. Anything is welcome even if it's only a friend to talk to, or fellowship from this community I've found.Thank you to anyone who's taken the time to read this long plea, because I'm sure it was rather incoherent, due to how distraught I've been mentally from all this, and I'm sorry for that. If you've read this far you truly have my thanks from the bottom of my heart. If anyone wants my additional contact information or anything like that for further contact, I'm completely open. I need help of any kind