So how much of Germany is coated with Anthrax?
As I read it, every city above 100k(+-).
Around 2,800 square miles is heavily contaminated (meaning they are utter "no go" areas for unprotected troops). Two areas around 30 x 30 miles centered on Berlin and Nuremberg respectively and around a thousand square miles of agricultural land outside of Munich (which was itself struck with a 150kt bomb).
There are larger areas with scattered, but noteworthy, local contamination surrounded these "hot spots" that total around 15% of the total land area of "Inner Germany". This doesn't count the regions with radiation from fallout or the wide swathes of the country where the biological agents the Reich released in France have rebounded and infected Germany.