I like the show but I agree with you on the ridiculousness of low ammo and the scarcity of guns. Maybe if the story was taking place in England then maybe that story line would fly, but not in the US and definately not in the South.
When most of the population is zombies guns would be easy to find.
The trouble is getting out and finding it. People don’t have the luxury of window shopping. And after a year or two when people have raided all of the stores and not used their ammo wisely - it’s going to get harder and harder.