Yeah, starvation hits really hard. Actually, everything hits hard on nightmare mode, since the RNG is stacked up to roll bad events constantly, from farm blights to rival gangs to zombie bites to a lot more. Majority of them are preventable once you get the right building and upgrades but they still hurt a lot in the beginning.
Yep!
Keeping a high defense probably cuts down on survivors dying to dogs/whackos. Perhaps barricading malls?
From what I understand, having a hospital takes away alot of RNG deaths, and researching zombie vaccine cuts down too
Pesticides and preservation tech keeps all your food from rotting away
Because it is never a good idea to mass convert or mass build, usually 5 builders is all you need.
Eh, I disagree. After my fort is under 10% danger, I'll organize my remaining groups of soldiers into 5-enough to take out a medium infection usually, once they clear out, I send in two builders+1 soldier, and the squad goes on another cleaning mission, rinse and repeat.
As long as you have enough defense, you can easily take multiple squares at a time, and can afford alot more builders. Of course, building toward the closest edge of the map is a good idea. Things get hairy when you don't have enough soldiers to defend everything.
Which is where a school comes in! Trading in units your not using, like scientists without a lab, no skill civs or extras leaders into soldiers is always good.