When George enters the supermarket, he is holding a flashlight with his rifle. When he reaches the propped-open back door, there is longer a flashlight on.
It's daytime as George approaches the soldiers. When one sees their campfire, it's dusk. Then George is pictured in pre-dusk. The the campfire is seen at night.
George 'leaves' the dude with a zombie, chained, separating duded from his house. He could simply walk around the tethered zombie.
Amputation of Megan's arm would not stop the (zombie) virus, as her blood would already have circulated sufficiently so that the virus would be throughout her system.
Five soldiers firing at George running away from their campfire, cannot score a single successful shot.