I clearly remember Elon Musk saying the BFR will be constantly accelerating to maintain gravity until the middle where it turns around start constant deceleration intended to keep gravity as well. The 0G would only last while orbiting and when turning around in mid route to switch from acceleration into deceleration.

I generally agree with most of the points, but I think small colonies are feasible, similar to the Antartica bases. If they build underground, the radiation and weather issues would probably be mitigated. I would guess if they happen to find some valuable mineral (ie. Gold) things would move on nicely (and the gold price would go down nicely as well...).