No time to explain, just look!
Comments from Pete Hines, Bethesda's PR-in-chief:
1) Yes, that's in-engine (in-engine means it's done with game assets in our rendering engine, but isn't done real-time. If it was done in real-time, that'd be gameplay footage. This isn't something, for example, that was sent to some house [e.g. Blue Studios] so they could build assets and render it out, and create something for us to release [e.g. Dawn of War 40K intro cinematic]).
2) Yes, that's The Ink Spots singing "I Don't Want to Set the World On Fire"
3) Yes, that's Ron Perlman [voiceover man extraordinaire of Fallout 1 and 2].