Hello Stephen!
I got an Austrian "Einzelgenehmigung" for my '56 Flash last year. If it helps you, I can send you a copy of the document via email. At least the noise level is in there (101 dBA Standgeräusch). I guess the German TÜV will accept an official Austrian document as proof?
They didn't care about the other two points you mentioned, but they wanted to see was a passenger grabrail or a band around the seat (your belt works well for this
) and they needed proof about the top speed (because of the tire type, had to call an approved expert, Sachverständiger in German, to tell them).
Oh, yes, they also didn't like the side stand, because it doesn't return by itself, so I just took it off right there.
And the guy thought it was a good idea to take it out for a test ride. I nearly burst in laughter when it kicked back and bit his leg
Regards, Markus