The Gun Runners had already set up shot and were making good weapons in Fallout 1, only 70 years after the bombs dropped.
That means they've been in business for over 120 years at this point. They've probably pumped out a LOT of ammo by now.
This. It's fun to think about things like this, but when it goes to "omg beth stupid FFS" stuff then you have to stop.
About the cigarettes, maybe wastelanders do those? They grow tobacco themselves and roll those, easy.
About the food. Well, in fallout world they probably invented some super-duper thing that keeps the food eatable for 200 years. They have fuel that last 100 years in power armor, so some food stuff should not be so hard.
About the other stuff, SCIENCE!