Re: Zombie Science, that's just it - most zombie movies don't HAVE to worry about that stuff, since the movie's over in two hours.
Here we have an opportunity to really take a good look at how the world will remain dangerous in a reasonable time frame. It's been (I think) less than two months since the outbreak in story time, and the population has already been decimated - we just aren't seeing much of the people who've been made into neural chow, where we probably SHOULD be seeing many more skeletons and remains of the devoured. I believe that the comics establish the changes in zombie behaviour and ability as the rot and winter set in, but that may be spoilerish.
One thing that's always been unclear to me about all zombie flicks - both this one and on the big screen - is how walking dead people could successfully overtake armed living people with guns, flame throwers, drones, and even nuclear weapons
Why wouldn't after the government realized that the world was falling apart would they mass exterminate the problem with more devastating weapondry?