Ah, yes, intelligent questions! I did say "the bigger the number, the greater the break." Balls amount to 0 break when they are stationary along a given line. Slow balls may be counted as 1/2 or 1/3, or even less, according to experience. Same goes for faster balls, which can go from 1, moderate, to faster and faster, with corresponding higher numerical values.
Again, experience is key in reliably attributing the right numerical value to the travelling balls.
As for the line crossing the flag, like the one crossing the ball, it is part of the relevant path to the hole and must be counted. Sometimes the line is a bit behind the ball or beyond the flag, and that has to fit in our estimate, adding subtlety to it.
So far, in practice, my formula has proven solid, but nevertheless leaves room for human error, in gauging and execution.