Ok, first things first, this is mostly related to Fallout 1, but what the heck.
About the Glow. Yeah, it was an old US military base nuked during the war (or it was a nuke testing gone wrong, i'm not 100% sure about that).
Now, as far as I was able to figure out, the war itself started because the AI in charge of the nuclear weaponry went berserk, so the AI is responsible for the war. The lack of resources itself, however, just led to another Cold war, this time with China. Again, this is my presumption, which probably isn't correct.
Anyway, you can beat the computer down there, but you need very high intelligence and you need to make a luck roll, but I don't know exactly how's it achieved because I actually never bothered to beat the computer.
Now, off to something I'm mostly sure about.
As you already know, the vaults were a US project developed to protect their inhabitants of nuclear blasts and radiation, but they were actually a massive social experiment. Some vaults only had men in them, some didn't have enough supplies, some had too many people in them, blah, blah. Anyway, the Enclave is the remnant of the former US government, so that's why they know all the details about the Vault project.
Now, why would the government do something like that... Well, if all vaults were intended to save the population, there wouldn't be an interesting background to the Fallout storyline.