White vinegar is apparently OK because it's been distilled... but I wouldn't use a cider vinegar anywhere near my mead because often that DOES still have the bacteria in it.
Fortytwo, I'd suggest replacing your cloth with plastic wrap once the fermentation dies down, keeping foreign matter out is one thing but after the yeast is done breeding, you don't want to let too much oxygen near your must.
That said, I've found that JAO is pretty resistant to oxidation, at least once it's been racked and you don't need to worry about any fruit sticking up out of the surface.