I wonder if I can do the 600 square ft floor over a regular weekend.

Not unless you have at least one very handy helper.

The living room/dining room is very open. It may be a challenge.

Close off your working area with taped-on polyethylene film. Keep opposing
windows in the room oen for air flow or use fans. PU finishes are nasty for
solvent fumes (not the water-based, of course).

Also what about using the rotary sander?

Don't get fancy, just use the conventional belt sander and edger from the
rental place.

I think I should do it before the weather gets cold.

Definitely, since ventilation is an issue. Wear proper safety gear, dust mask,
etc. HTH

Joe