Regarding Sales Reps, what is their commission percentage structure based upon, Gross Profit, or Gross Sale? How do the reps get credit for the customers and sales they have brought in?

This is based on the Gross sale. When a sales rep shares their unique URL and someone comes in and signs up via their URL then they will be linked to that sales rep every time they place an order. The sales rep will get a percentage of the sale. You assign the percentage to the sales rep in their profile.