It's probably very complicated, but I would answer yes to many of these questions. I think it would be worthwhile investigating a model where every home has a mini-grocery with affordable prices within 2 blocks of every home in these neighborhoods - and to achieve affordable prices, there may have to be some tax breaks involved, with some accompanying price limits on "staples" (bread, milk, etc). Difficult, yes; impossible, no; worth it, I think so.
Come to cities in Germany. Everwhere I lived the next supermarket was less than fifteen minutes walking away. Price and density are inveresly proportional.
"Every two blocks" is a bit much for anything but the densest of high-density areas. Even the convenience stores aren't clustered that closely in my city's downtown.
