2 players would be enough if you are sure you can both come every single time. Having some replacement guys might be a good idea.
It's one BO3 per week. 2:0 gets you 4 points, 2:1 3points, 1:2 one point and 0:2 zero points. A walkover is -1 point for the loser and 4 points for the winner. There will be six teams in one division, each one plays every opponent once in a season.