Loss of utilities does not result in instant collapse of society.

It absolutely does. Most US cities only have enough total food for three days, regardless of size. There are case studies of cities in China that run out of food. The first thing that happens is the annihilation of local animal populations, then starvation. When you're starving, you either die and fight, and most people would do both.

Does anyone know the ideal crop for sustenance in the case of a nuclear/volcanic winter.

Rhubarb springs to mind, grows well in cool climates and denying sunlight produces a better crop.

Any others?

Edit: the book recommends stocking up on rice, beans & grains.

No lights. No refrigeration. No gas pumps. No communication. No vehicles.

The collapse would not only be instant, but within days there would be mass starvation and chaos.

People underestimate just how fragile civilisation actually is.

From the description at the top of the thread it's as if we'll just come out of our shelters after a week and everything will go back to normal, we'll just drive down to Arby's for dinner, maybe catch a movie.

More people need to watch Threads.

Do EMP's affect generators that are not running during the blast?

No, but they will affect most of the equipment connected to those generators.