Can't answer all of your questions, but here's a start:
AFAIK, the E and S mode trannies went with the V8's; as yours is a 6, it will probably have a different tranny and definitely a different rear axle ratio--which would be the reason for the different RPM at 60 mph. A smaller engine typically will have to work harder for its living, and will be geared to turn higher at a given speed.
4Matic was the name MB used for their 4-wheel-drive system; cars that have it typically carry the word on a trunklid badge.