how much is the discount for state and local government employees and which products qualify under that program

It also varies with where you are in the world. Some discounts may only be available to US users, although Apple sells internationally.

Remember that you are not asking Apple here. We can give you links to Apple articles and policy statements, but not an "official" answer.

Varies by product, and you need to go through the Apple Government. See here: link-> Apple Store for Government - Apple