The User can be associated with the Waiter Entity automatically upon login using Automation, so there is no need for entering a PIN twice.
Create an Action of the Type Load Entity.
Create a Rule for the Event called User Login, and within that Rule, fire the Load Entity Action using [:UserName] as a parameter to the Action.
To assign the Waiter to the Ticket, create an Action of the Type Change Ticket Entity.
Create a Rule for the Event called Ticket Created, and within that Rule, fire the Change Ticket Entity Action using {:CURRENTUSER} as a parameter to the Action.
Yes, you can use Custom Reports to pull just about any data your heart desires. That said, the Work Period Report already shows Sales based on Users.