Are the specific actual rules of the Rank Meter known?

From the Splatoon Wiki

The rank meter is represented internally as a number between 0 and 100. The numbers that track filling of the rank meter and those that track cracks are two separate systems; winning matches adds points to the number system that fills the rank meter, while losing adds points to a different number system that contributes to cracks on the meter.

A full rank meter is represented by the "fill" number reaching 100, which causes the player to rank up. The rank meter breaks when the "crack" number reaches 100. Every 25 points is equivalent to one crack on the meter.

How the player gains points that affect these numbers depends on the probability of winning a match in Ranked, as determined by the game. The number of "fill" points gained for winning a match that the game determined was a likely victory for the player's team will be lower than that gained for one with a lower probability. Conversely, losing a match that the game determines the player had a high chance to win will add a high number of points to the "crack" number compared to one where the player was less likely to win.

(emphasis mine)

So what the wiki seems to be saying is that the cracks merely serve as a visual indicator for the second number, much like the progress bar. I was unable to find values, but it probably has something to do with the difference between the ranks of each team and not just random chance.

To answer your questions:

(1) You get a crack for every 25 points in the "crack" number

(2) It moves an amount determined by how likely you were to win the game.