The formulas are:
prob = 1.0 / (1.0 + Math.pow(10, ((opponent.elo - player.elo) / 400)))
deltaElo = k * 3 / (numPlayers + 1) * (wlt - prob)
The player's winning probability against the opponent is prob.
wlt states for win - lose- tie. Can be 1 - 0 - 0.5
For each player we calculate the deltaElo against each opponent.
If the player and the opponent both dropped, the deltaElo is 0.
If the player dropped, his wlt is 0, regardless of the score. Therefore the player loses k * 3 / (numPlayers + 1) * ( - prob) Elo points.
If the opponent dropped, the wlt is 1, regardless of the score. Therefore the player gets k * 3 / (numPlayers + 1) * ( 1 - prob) Elo points.
If the game is a dropped game (i.e. someone else dropped), the deltaElo is 0.
In the other cases we calculate the wlt base on the scores, and the we get the deltaElo.
Back to your questions.
You are right. If you are not the only one that dropped, you save some Elo. That's why we introduced the ability to cancel a game. If someone dropped and the other players don't want to finish the game, they can cancel that game. In this situation only the dropped player will lose the Elo.
Anyways, dropping is not an option to save your Elo.
Let's say you have Elo 200, and your opponent has Elo 400. In a 1vs1, after your 20th match, you are getting 15 Elo points if you win. So, it's difficult to go up, but in the long term you will reach your Elo.
I hope this helps!
