Data modeling architecture

1. If as you say there are no records of the employees with regards to who made the sale.  I don't see that there is anything to do or can be done.  If there is department info in sale - all that can be done is link/report all employees of that department.

2. You will have a Product table.  It is a matter of design choice whether the Product table includes ingredient info - or - whether you have ProductIngredient table with a relationship join.  Usually the tables come from database applications and so the Power BI developer begins with what is given to them.  So it is a little unusual to confront this issue in Power BI.

3. While I don't quite understand the difference between sales process data versus order data; generically speaking if your reporting need is only to the day - and not to the minute - then one just ignores the time info;  if it is to the minute then one would have to invent & use a default time where none exists.