What are the proportions to make a cup of hot chocolate?

Depends on how you like it’s strong or not. I use 2 full teaspoons for 10 oz whole milk. If skim milk or 2% maybe a little less.

What is the expiration date for this product?

Hello, the expiration date is december 18th 2023

Is this "Dutch processed" as called for in recipes?

Coenraad Johannes van Houten was the chemist and chocolate maker known for the treatment of cocoa mass with alkaline salts to remove the bitter taste and make cocoa solids more water-soluble; the resulting product is still called "Dutch process chocolate".(from Wikipedia).