For number 1 and 2 you need to aggregate you query to customer level. Set the customer ID as a dimension.
1) Have you tried binning your product sales?
You can create a bin with increment 1 and you will get your results.
2) Just create the rule on the sales metric without using any sums in the formula.
I tried doing it but was unable to get the desired results. (Or maybe I have not done it correctly)
Do you have an example that you could share.
Give me your .tbw-file and let me see what I can do!