1. I don't think age matters, I mean Watup and Chan are great examples. Both are much younger than myself and easily surpass me in skill, hahahah. Same goes for older players. I think what it all comes down to is how much time you have to practice/how dedicated you are.
2. See #1.
3. I'd have to say (from what I've seen) the 13-15 is what we have the most. But the total average of players would probably be around 16-17.
4. Dogfight isn't as intimidating as other war games. I mean, you boot up Call of Duty with no past experience -- and within seconds you'll find yourself with a knife in your back. I'm not too much of a fan of any of the Call of Duties -- especially those on console. I own them, but I do not participate in the multiplayer. All the REAL good Call of Duty players play Call of Duty 1-2 on PC. The sniper servers are the best. If you get up and even attempt to run'n'gun, you'll find yourself shot in literally seconds. Plus the players are much more mature than the idiots on Modern Warfare/Black Ops. Anyways!
5. It's general guys who take interest in war. As a very young child I was always reading WWII books, I saw Saving Private Ryan at a very, very young age (LOL), and more. I've always just found war, tactics and other aspects extremely interesting. Especially weaponry.
Just as it's somewhat rare to find a girl who knows her guns -- I think the same goes for Dogfight. Even though Dogfight isn't your generic "shoot 'em up" game.
Just my thoughts.