how to balance risk/reward
Humans are notoriously HORRIBLE at making risk assessments. I think you will see that some people did try to come up with a 'creative'/desperate way to stay warm by running their car and died due to CO. Is that bad parenting or just an uneducated mistake?
when you pack people too close together
That is actually a good source of heat, I see you're on to something!
People suck, and you don't want too many around to get in your way of saving yourself and your family.
With that mindset, you may as well admit people are at least a food source. (In case the sarcasm is missed, cannibalism is actually a bad idea.) Also, do you realize your family is made of people? If you employ a little more compassion, you might realize that other people have families too and you could work together with them to solve problems caused by emergencies WITH them.
"May your future be limited only by your dreams." -- Christa McAuliffe