1) this basically comes down to a variables question, you have to make individual integer variables that keep track of each player's kills (via the 'unit dies' event). And then you need to keep track of the teams kills by simply summing all the individual player kills together. You should automatically know which player numbers are on what team, so that won't be hard.
As far as I'm aware, you can't get a leaderboard which displays team kills, player kills AND sorts the kills in numerical order. It's pretty easy to just simply list them, however, the structure would look something like this: (e.g.)
Code:
PLAYER KILLS
player 1 23
player 2 41
player 3 12
team 1 76
player 4 13
player 5 22
player 6 12
team 2 47
just remember that, if you need 2 lines to put team kills in, then if you have a 12 player map, those lines need to be allocated probably for neutral hostile and neutral passive or something like that, e.g. add (neutral hostile) to (last created leaderboard) with label (team 1) and value (team1kills)
i'm assuming here you know how to do a basic leaderboard, cause you're not specifically asking how to do a leaderboard, but how to do it
a certain way.