#1- There have been a few posts on this recently, it's a common occurrence i think
#3- just deal with it. I had brake dust covers on my '88 420SEL, and they caused excessive brake fade, to the point I had trouble stopping at all. Do your best to keep 'em clean.
#6- To remove the light, push the entire assembly to the left (push fairly hard), and pull down on the right side. The owner's manual says to push to the right, but I found it easier the other way.
#8- A/C work is expensive. That's all I can say.
#9- Just dry it off, I think it's just a design flaw, mine does it on the drivers door.
#10- Can't tell you the measurement, but I think the only fix for that is new springs. Common problem, I see it a lot on 126's.
Hope this helps.