I've actually pulled this off against the AI before. You'll need to have a map with multiple solar system with at least one of them without another player. I was getting ganged up on pretty bad so I built a colony cap, left town for biggest neutral system (You might need to leave three civic labs intact, I don't remember if the tech to jump to other solar systems needs the labs alive or not), and scuttled everything else in the starting solar system. By the time the AI got around to my new system I had colonized the entire system and easily managed to repulse them, and then sent a massive invasion their way. Sense it was the resources of my one solar system versus the resources of the starting solar system with 5 AI in it (with no alliances), it wasn't much of a challenge.

No it doesn't.

Fleeing to another location is a great idea when you're going to lose your empire, but it only works in team games or FFA scenarios.  If it's a 1v1 you're screwed.  By the time you actually get a new economy up and running in your new home, your enemy will be bearing down on you with a fleet of certain doom.

Now that's more like the Advent!