4, Plan for camber adjusting:
When inspecting the tires I can see that the right tire is a little bit more worn on the inside.
It could be that the camber angle is too much negative, the wheel is tilted inwards.
But on Mercedes SLK R170 the camber angle at rear is not adjustable.
You have to replace a control arm with an adjustable one if you want to adjust it.
Upper control arm:
This upper arm (behind the stabilizer bar) is the one that has to be adjusted in length to correct the camber angle.
It's not possible, it must be replaced by one that make this possible.
Normally there are some worn rubber bushings that cause this problem and they should be checked first and replaced if needed. The car can also had an accident.
If you lower the car a lot the camber has to be adjusted, also the toe in / out angle.
The latter is possible to adjust as it is on one of the lower arms.
The outer pivot point of the upper control arm.
The other side of the same bolt, the nut that has to be loosen when replacing this arm.
It can not be done without some other part are taken away, beware of the spring and the strong force it's compressed with.
Don't do anything by your self, it's very dangerous.