The individual games determine the ranks, not the whole match.
You can quit between games and not lose elo
You get matched with the same person 10 times in a row
1. Changing this would increase the gap between better players and worse players, not help at getting rid of current ways to exploit the system. Those who are currently top 50 will lose ELO even less often -> the more they play, the more elo they get (same as now but worse).
2. Will either consider elo penalty for quitting mid-session or other sort of punishment when a player had significantly less fights in a certain mod.
3. Already addressed this in an earlier post.
"Our" elo algorithm is the regular elo algorithm.