Hi there.
I guess for now, you should stop picking fights with your brother, give in or something man you guys are kins. For goodness sake, your father is old already and he trusted both of you to be mature enough to live together, away from them that is. So the more you should prove to them you can do it, at least not make them worry. Moving back is definitely not one option you have considering the distance, but what you can do it perhaps spend more time with your parents during weekends? Cut down on computer games or consoles, spend more time with your family, that is definitely more meaningful.
I feel that they aren't really sad because they're disappointed or anything, they're sad cause they fear you can't live well, for instance with your brother. He is just worried, like what all parents will react. Lol catch a movie with him occasionally and make him feel that you're alright and enjoying man, it really helps. Though speaking for myself as well, it is hard for youngsters nowadays to make parents understand "their" world, but watching a movie and spending more time to talk won't hurt right?

Good luck.
Cheers!