bones
On your third point can you post a picture for us to look at.
On the other points I've not experienced any of these issues on my S4. Has it been serviced recently, maybe a loose hose, are you smelling the fuel in the car, under the bonnet (hood) or just in one location?
Now I don't want to make you appear foolish but I had a similar clanking issue in a classic I owned. Spent hours trying to figure out what it was only to find a screw driver tucked deep in the boot which was bouncing off a piece off metal in the boot floor
