Q1: Yeah, battler are a chaotic, At a bit higher tiers people tend to be a bit more smart (sticking together, covering bombers), but no, it stays like that (F2P game, what do you expect)
Q2:You earn 4 types of exp (well, not really, but it will be easier to explain)
1.Your general rank shows how much total XP you gathered in general (quite obvious). Total XP you get from a battle goes there.
2.You Air force rank determines what planes you get, and you also unlock single player missions. The higher the air force rank, the more interesting shit you get (like tiers in WOT). Its quite cool because you just have to fly for a certain nation to unlock more planes, so if you don't like a certain plane, you can just skip i t and play the other ones(a fighter you don't like for example). Just like General rank, total XP from a battle goes there but only to the nation you were playing.
3.Each plane you were playing, also gets XP, When you gather enough XP on a plane you get various unlocks for them(apart from rank 0 planes, they don't have any unlocks), some planes have mor of them thanthe other. You gain plane XP for basically doing shit with it (you can check stats after a battle, and see whats what, just)
4. Crew XP. Basically its like plane exp. only its for the crew ,you get it for killing stuff etc. After a battle you get XP point that then you can spend to skill up your crew (cost of skilling up rises slowly, at the beginning it takes 1 XP point to get 1 skill point, but then it changes to 2 for 1, 3 for 1 etc.)
Q3: You can have as many planes as you want. There is no limit of planes you have, BUT there is limit on crews. Basically you start with 3 planes and 3 crews with each nations. Whenever you got to battle, you go with these 3(your whole line up), one gets shot down, you pick another one etc. But you can buy more crews, to have more "lives" per battle (you can have better choice of planes, and you can fight longer), You can have 5 crews per nation without spending any real money. You can always change the planes in your line up whenever you want