it never works out well when you try to micromanage stuff like this. it only works in games where a computer tracks it for you. it becomes accountant the game.
just words of warning.
instead, Ctrl+f "Mojo" in >this< document. (i'm only recommending that section, the rest probably you don't need)
This removes magic items and money from the system entirely(though you can still find magic items are rewards). Instead of getting their floating inventory from a market they get it from scavenging.
this will get you the verisimilitude you want and remove the weird complications of you needing money and magic items in this game.
Agreed with Bandw2, in a post apocalyptic setting scavenging through ruins and finding stuff is where you obtain equipment. Really, in a "just trying to survive" world, crafting goods is more a settled world activity, so would be the absolute minimum. You'd spend time crafting basic weapons, basic armor, clothing, survival gear - not creating magic items (that doesn't make any sense at all).
The Survival skill already has a check for hunting and gathering. You can just use that unless the environment is totally different than normal, like a radioactive desert (DC +10) or an abandoned Wal-Mart or recently deserted noble menagerie or the royalty's stocked hunting forest (DC -10).
Honestly, micromanaging PCs' calorie consumption just isn't fun, and basing nutrition on CR is just plain wonky (a CR 13 iron golem is a lot less tasty than a CR 1/4 deer--unless you're a were-rust monster!).
One thing you can do that IS fun is have some types of animals have special items. For example, maybe the heartblood of a dire bear is equivalent to a Potion of Cure Serious Wounds. Maybe the antlers of the (probably unique) albino stag can be fashioned into a +1 composite longbow. Stuff like that. Make things special for the PCs, since they are the stars. Just don't allow industrial slaughterhouses of domesticated dire bears to mass produce Potions of Cure Serious Wounds. And by "don't allow," I mean run a campaign where the characters (PCs AND NPCs) wouldn't be inspired to do that, as opposed to using DM fiat to ban factories or dire animal husbandry.