Hi Matthew,
inlet valves 0.10 mm, exhaust valves 0.25 mm, clearance values with cold engine.
When you have the cylinder head bolts accessible you can certainly loosen and re-torque them one at a time. I have done this once, not knowing the full history of my engine. This should however not be considered a service interval job.
Regards from Ingvar in Sweden
109.018.12 1968 Bronze Braun (M100 in good shape)
126.039.1A 1988 Dunkelblau (M117 so a bit slower)
+ A few other MBs used for daily transport