Network television ratings for professional football games are falling, and the NFL is concerned.In fact, the league is concerned enough that it’s looking at changes to make broadcasts more fan-friendly — and most notably by focusing on the way commercials air during games.Given that the priciest 30-second TV commercial averages $674,000 during NBC’s “Sunday Night Football” (according to Advertising Age), when NFL executives consider tinkering with TV advertising, you know they’re …