As someone who has also felt "unlucky in life" myself, I sort of get this. I've also seen, and felt, that "some people get every thing in life and the rest of us get a miserable life". I don't think it's insane to feel this way. It really does feel like life is a two-tiered system at times, between the "haves" and "have nots". And sure, it's possible to jump from the "have nots" to the "haves" as in, people have done it before. But it's not easy, that's for sure. It can drive you to the brink of sanity.
It IS frustrating to see others just get handed the good stuff in life, without having to change themselves or work on themselves or think at all, they get it all just for being what they are naturally - especially when these people are awful on top of it, when they're "sore winners". Meanwhile for you, it doesn't seem to matter what you do - whether you bust your *** or not, you get the same "nothing" anyway.
And I never understood why people who aren't doing well, aren't allowed to complain. It always seems like if you complain, other people, who often aren't doing that great themselves, come out of the woodwork to defend the system that makes it this way. That never made sense to me, it's like, you're all being screwed by it too, why defend it? Is someone having a hard time and disliking "the way it is" really that hard to understand? I don't get it.
However, I'd also say that if someone is causing you this much pain and heartache, then it's not worth having this person in your life.
If seeing someone posting complaints about their life, when you think their life is perfect, bothers you, I would just unfriend/delete/block the person, rather than get re-aggravated every time they posted something like that.
Also, I would say that you can't please everyone in the world - some people are going to think they're better than you, because they're just jerks. There will never be anything you can do to impress these people, but then again, if they are such jerks, why would you want to? I know I wouldn't want to be friends with, or date such a person, because I wouldn't like them at all in the first place.
The way the guy talked to you is terrible. I say, if that's the kind of person he is, let him go with his jerk friends. I'd say, have some self-respect and pride, and cut off anyone who talks to you this way. Show that you're not going to take it - not for them, but for you - to feel better about yourself.
This guy sounds very spoiled and a total jerk, and his problems sound like the most "first world" of "first world problems". If I was OP I wouldn't bother with this guy, and after talking to you the way he did, I would tell him to f*** off. One thing I learned that I wish I realized earlier, is that there's no point trying to fit in where you don't belong, where you're not compatible. And also, that I wouldn't have enjoyed hanging out with "the cool guys" and "the hot girls" anyway, so I didn't even miss out on anything I would have enjoyed, anything I would have really wanted. I only thought I wanted it. That's the thing, society says that how close or far you are to being one of "the cool guys" or "the hot girls", is how "right" or "wrong" you are, how "superior" or "inferior" you are. But it's not true. What it really is, is similarity, compatibility, like-mindedness - finding people who think and feel the same way as you. That's the group you should be going for, cause that's the group you'll fit with.
I would say, DO worry about being healthy, stylish (in a way that's authentic to your interests and personality), and interesting, but DON'T worry about being "cool", "popular", in the "in crowd", dating the "hot" people. Try to make "you" awesome, but don't worry about trying to conform to society's ideals if they are not also your ideals - chances are it won't work anyway, and you wouldn't even be happy with it even if you got what you thought you wanted.
It's too bad I couldn't have talked to OP at the time, I think I could have talked them down some.
However, it would have to be the "me" as I am now, with the realizations and perspectives I have today.