My experience with clutches with Mercedes is that they tend to wear with the release point moving higher and higher.
If your clutch slips and has a high release point, it sounds like it is worn out.
I have had both good and erroneous measures with clutch wear tools.
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)