Secondly, I'd like to know how many of the apps that Heroku hosts are actually production apps.
Agreed. Because of Heroku's unreasonable pricing, I see it as a feasible service only for staging and development. Without deep pockets, I would never want to host a potentially popular app on Heroku since I could never afford to scale it there. And because I don't want to have to go to the trouble of reengineering something after it's been developed to move it elsewhere, I would rather build it elsewhere from the start.