I talked to the Audi dealer today... Their RS certified tech said that there is nothing that should be damaged by either E85 or bad gas if not driven under heavy knocking. At worst, top off, drive it down to half a tank nicely, top it off, and repeat a couple more times before driving it hard.

It could stir water in the tank, which would basically go away after a tankfull, it could also stir debris due to varying density (heavier than gasoline) that could block the filter. They said it should actually be good for the injectors, rails, basically everything after the filter. He went as far as to say that some companies use it to clean fuel systems, basically dumping 3 or 4 gallons of E85 into an empty tank, drive it 25 miles carefully, and top off with normal fuel. Worst case should be a blocked prefilter in the tank.

Now on to my next problem... The threaded at the top of the fuel pump bracket is turning with the bolt, so I may have to cut and replace the bracket. Anyone have an idea on that one?