He's stated previously regarding just the bunker, that it'd be sold as a bunker with a house, not a house with a bunker. That arrangement is apparently more valuable as that makes the house much more desirable for the type of person interested in bunker-digging.
I'm not sure if the tunnels change anything, but assuming they're up to some sort of code, probably nothing.
I think so. IBM recently produced a new "5nm" chip. In reality the physical size is closer to 24nm, if I remember correctly. The numbers you hear don't literally mean the physical size of the transistor, it refers to something else.
Definitely. I'm not sure how you'd expect anything at all to function without power, water, food, messaging, etc would all be gone. I'm not sure how it'd be possible to survive if you're in a city.
I've personally been in voice calls on discord with thousands of people. Obviously it's impossible to pick out anything discernable with that many people but discord handles it well.