I actually use a 1/2 cup per box, so for hives that have 2 boxes I use 1 cup (1/2 cup from each box). I don't agree that alcohol wash is more accurate, in my experience I got better results with sugar shake. (alcohol wash is faster, sugar shake takes time)
About killing bees, I don't want to kill bees unnecessarily when they can be useful for the hive. For a small hive, like a nuc, 300 nurse bees can be very valuable.
I always record my mite counts as percentages rather than a real count. So I don't have to record how many bees were used. Any time mite count exceeds 3% I know I have a problem. This year I tested all my hives monthly and the percentages were below 3% until last test on August 26th. I treated all hives that had % over 3. Two hives still have less than 1%. I will be testing them in a week and will treat them only if the count is over 3%.