On a normally functioning brake, you will hear a dragging sound, as the brakes do rub very lightly.
When you spin the tire, it will not go on spinning forever, as long as it turns relatively freely, it should be ok. Usually getting 2-3 turns out of a wheel indicates that it is ok.
The true test that I like to do is to get out on the highway drive for 10 miles or so without using the brakes and pull into the next highway rest stop at the earliest convenience. When you are slowing down, do not use the brakes, engine brake the car all the way down to below 10 mph, then use brakes to stop. It is important that you carefully engine brake the car all the way down to a walking pace. Now, you have been on the highway without any brake use and you did not use the brakes to stop the car. All brakes should now be cold and all be the same temperature. If a brake was rubbing due to a stuck caliper, that rotor will be hot (just be careful not to burn yourself).
H rated tires are fine, they are good up to a speed of 130 MPH and the C class is governed at 133MPH, so I do not think there is any need to go to V rated tires.
Also, I did not mean to automatically condemn your tires. Continental does make good tires, I just suggested to possibility of wanting to purchase Michelin tires and for you to check your tires to make sure there are no flat spots. There is no need to keep spending money on the car, unless you really want Michelin tires.
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record