best check those items, lift the car and tug on the tie rods to see movement, the ball joints require you to unload them to check - raise the car and put a support under the control arm so that the car comes to rest on that support, now lever the joints up and down, if you feel a movement replace the ball joints immediately.
the idler arm is checked with car on ground and someone turning the wheel, if you feel it even move a hair then its bushings are shot.
usual cause of highway swaying are the rear subframe bushings - you can look at the front edge of the rear fender to see them, if you can move them with a tyre lever they are worn out. What happens is that the car skitters from the rear causing you to correct direction again at the front.
the excessive slop in steering is usually a case of bad joints, look up my thread to find how I replaced them on my W124 - its the same on a W201.
best change the stabliser shock every 4 years anyway and repack and check the front wheel bearings too.
did you get your car aligned recently or install some wider tires by any chance?