It's not easy being a teenager - I'm sure we all know and remember feeling that everyone had it better than us and life was so hard and unfair, and it is only afterwards with better perspective and less self obsession that you realise how people were just trying to do their best by you at the time.
But instead of seeing everything your dad does and says as a negative, try and see the positive in it. He told you that he once did drugs when he was younger and you are now using this against him - instead look at how positive and honest it is that he can tell you that - there are a lot of parents who would not have that sort of discussion.
You complain that he feeds you all the wrong stuff - have you talked to him about this, but also as other people say, he does seem to be trying his best to feed his family well and look after them. Or as other people have suggested, offer to make tea a couple of nights a week - ask if you can have the money to do the shopping for those meals (good experience for when you move out on your own tell them) and convert them to more healthier living,
I know that when things feel bad, it is often no consolation to think well it's worse for other people, but it really is - I work with homeless young people and they would tell stories that I think would help you put your concerns into perspective - and a lot of what you are concerned about (the food) can be fixed by you - eat less of it and exercise more, if you are worried. And maybe, even if you can't get a job, you could look at some voluntary work and get some perspective on life to see that things, as you decribe them, are really not that bad at all.