1. The 15M number is massively inflated for unique viewers, as the game was auto-playing on the Yahoo! and tumblr homepages. More detailed breakdown of the numbers here: http://deadspin.com/not-nearly-as-many-people-watched-bills-...
2. The NFL will not be rolling out a la carte streaming packages any time soon, as they have a preference to selling exclusive rights at a premium, e.g. - DirecTV has exclusive rights to broadcast all games, and stream all games digitally through 2022 (http://espn.go.com/nfl/story/_/id/11624442/nfl-extends-sunda...) - Verizon has exclusive rights to broadcast all games on smartphones through 2022 (https://www.verizonwireless.com/news/article/2015/09/live-st...)
3. For comparison, both MLB and NBA offer streaming plans for all of their games, for reasonable prices ($130 for MLB, $200 for NBA). These plans are only limited in not showing local market games. They also have great app support (iOS, Android, Roku, "Smart" TVs, etc)