I don't think they 'need' 7 games. Your math is a little off for them according to Forbes; in 2017 their net football-only revenue was 21.9 million. If you want to just count tickets and game day contributions (concessions, premium seating, etc) it was 3.3 and 6.6 million, respectively. They had just 6 regular season home games that season, obviously 7 reg season home games plus post season would be higher. Therefore, they are earning at a minimum over 1.3 million per game just from tickets and add ons in 2017, it's probably significantly higher. 3 games is all they 'need' to break even on their rust bucket. In 2017 they were not getting nearly the ticket draws or contributions they are now I imagine. Their total football expenses that included everything from traveling to recruiting to debt service to coaching salaries was 18.1 million in 2017. It appears that even in 2017 their FB department was profiting 3.2 million after all expenses.
I personally agree with both USF's and UCF's scheduling philosophies. They both seem to be working.