TWAWKI includes foreign aid, UN troops, and eventual restoration of key services and supplies, in a matter of weeks or months. But for EOTWAWKI, you should be planning that every drop of fuel, water, oil, and every gram of gunpowder, metal, and chow are precious and not replaceable/renewable. You could burn up a decades worth of resources in just a few hours playing Rat Patrol, and get your mechanic/armorer dead.
You're also not anticipating the second and third order effects of an EOTWAWKI scenario, such as plague/viral epidemics spawned in part by the potentially millions of dead bodies lying around, or industrial meltdown like when critical machinery and equipment (national power grid, fuel stations) are left unattended. Then were playing Stop, Drop and Roll.
Who are you going to attack, and why? The ethics of post-catastrophe societies the world over are simple: attackers bad, all else good. Live and let live.
Unless were playing Red Dawn, then this isn't a survival discussion.