I can't help you with the stuff coming out of the ducts, the hood liner replacement adhesive, or the question on the turbocharger operation, but I can try the other two questions.
First, the ducts in the doors feed airconditioned (heated or cooled or both) to the little holes in the doors. This was a big deal in the advertising literature of the day, as the hundreds of little vent holes were supposed to "waft" the processed air through the cabin rather than blast you with a stream of cold or hot air.
Second, Mercedes to my knowledge has never officially endorsed Redline additives, and for a while the original version was suspected of loosening little hot chunks of carbon that were impinging on the turbocharger and damaging the blades. Thus the advent of the Redline '85 stuff, which was supposed to have some kind of formulation that would not do that. In the end I think Mercedes stopped using the trap oxidizers, as they were eventually implicated. I am not familiar with any of this actual hardware as none of my cars ever had a trap oxidizer. But I have poured a lot of Redline into my 350SD and it likes it. From reading this forum, I think there is yet to be a Mercedes Diesel identified that did not like the stuff. And you can buy it at Mercedes dealerships (that is where I learned of it in around 1982 or so) but I do not believe it is officially endorsed by Mercedes-Benz.
Hope that helps you, and it sounds like you picked up a really nice example of a great car. Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)