W210 Driveshaft Advise

[Southern]

My 98 E320 with 107K miles has a slight vibration (felt through steering wheel) from 45 to 65 MPH. I believe that I detect a slight backlash from the driveshaft when I come to a stop.

I thought that my flex disks were worn due to the age and miles on the car. I lifted the car up on all fours and did a close inspection. There are no cracks or movement when I twist the driveshaft by hand of the flex disks. There is a slight movement (rotational) from the output of the trans with the car in Park.

There is a slight movement (latteral) at the center support bearing. The movement is under 1/8". Is this normal or do I have issues with the driveshaft support? Fastlane lists a driveshaft bushing and a driveshaft support for my car, is the driveshaft bushing part located at the center support and is it usually replaced along with the center support? Is the heat shield held in place by rivits or are those threaded studs?

I believe that my flex disk may be an issue since I couldn't apply much torque on the driveshaft twisting it by hand. Since I would like to find the cause of the problem instead of throwing parts at it I would appreciate any advice.