Tendergreen or Tendergreen Improved is another good bush bean. If you keep the beans picked (don't leave any big buzzards on the plant), they will put on a second blush of blossoms and beans after the first is done. The second harvest is not as large as the first, but it is free.
I've never found innoculant to be worth the expense or effort. My general sense from planting beans anywhere from a 3" to a 6" center is that the total yield of beans is about the same. In a wide row planting of bush beans, they will be competing for sun, moisture, and nutrients and thus a certain amount of space supports a certain amount of production, in my experience.