It does look like a bit of carbon for just 9K, but it's kind of hard to judge. A lot depends on what kind of driving you do, kind of gas, compression etc. It's not terrible looking, but I think your plugs would be a better tell to judge how it's burning. Your milage sounds slightly on the low side (my 91 300E 2.6 gets about 18 around town/ 25-27 highway).
Personally, I wouldn't use any gasket enhancing materials unless I had good expert advise (which I can't give). When I was able to talk to that gasket designer from Reinz the two things I was seeking was info on the modification (which he couldn't give me) and advise on whether I could use a gasket silicone to repair the scrape on the gasket I had damaged. The damage was on the red silicone bead, on the top/outside edge around the last oil drain hole. His response was, that because of the non critical place where the scrape was, and that there was little pressure at that place, and that the scraped spot was very small, he saw no problem repairing it with a similar [high temp] silicone. Even with that, he advised me to merely fill in the missing material and not to build it up higher than the original bead. I used the black M Benz silicone as used for the front timing cover.