You could always jack the car up & spin the tires to see how bad the out of round is. You can visually see a hop in the tire if it's out of round. It will cause the problem that your having if tires are out of round.
True. Plenty of tread on the tires, but they are hardened after four years and sitting sometimes for 3-4 weeks in one place. At least one is out of round, since it is impossible to get the balance perfect on it.
As for the driveshaft speed, I am figuring that I am just over half of critical speed at 65 mph, which I wouldnt think is a big deal.