Lets play a game. Its called, make it true. When left with a conclusion that makes no sense , the simplest answer is true. Mutations- Well for starts this situation actually explains the biological condition of the planet in fallout. Under normal circumstances plants, trees and animals would have recovered to some extent after several hundred years. Unfortunately in fallout the reality that mutations wouldn't occur as in the game is false. This world it did happen, so any realities from our world become null to a extent. Since plants and animals did mutate the regular ecological process of regeneration didn't occur. That may take hundreds of more years in this system as animals and plants are forced to adapt. So on that account Fallout is what is it is. It doesn't persay need a explanation beyond it happened. Structural Degradation- Under normal circumstances food would have long since became inedible after 200 years. In the fallout world it is. Mostly due to the Abbraxo, pardon the mispelling, tech which they developed. Primarily the packaging most food is stored in is designed to keep material inside biologically inert. It mite look like cardboard. Its not. Appearances are deceiving. In the fallout world they figured out how to store foods in materials which effectively stop the biological process of degradation. The food is irradiated, lol ironically a good thing, then sealed in packages which are airtight and contain anti-biotic substances. Japan is actually working on technology like this which could store something like a rice noddle and be healthy 100 plus years. As for the houses, I imagine some explanation due to technology can be applied. The Anti-Biological process can keep wood preserved. As well as other infused materials may keep it intact. The tech in fallout is definitely based on the 1950's but also excedes our tech level in some ways. Food- The above raises a question though. If food can be eaten and preserved for extreme periods of time would any be left? Most likely very little. Even with extremely small populations of humans most of DC would have been scavenged. That being said food has to be coming from somewhere. Several high tech food production faculties are in the game. Especially rivet city. Enough to supply most of the food needs for the area through trade. I also think that one can assume many of the operations which are involved in food production are simply not being rendered. People do farm cattle. They just aren't showing it in the game. Maybe if we get a construction set we can fix that Overall the game can make sense if you simply remake the way you think of the rules of reality and live by a very different set of realities which fallout would require. Divergent realities can be very confusing. The only factor which is glarringly impossible to reason through is the food radiation! If you ate food which has rads, you would accumulate enough to kill yourself in months! The way they have radiation handled with food is abysmal! I don't even eat food because I know its useless. Either Rad-x was extremely common and stored almost everywhere and people are surviving via that or someone is making rad-x in large quantities at a pharmacy in a city like Rivet city. That or they got the accumulation rates totally bass arse backwards and it should accumulate a .001 rad per serving. Low enough to let people live into there 50 or 60's before dying. Hopefully someone makes a way to decontaminate the food in the game. Allowing a storyline element to be feasible. Perhaps a anti-radioactive element which can be added to food.