Translated from the German: Das Verhalten derer Soldaten und Unterthanen ... signed P.L. and issued in 1757 in a collection of Prussian army regulations with title Allerneueste acta publica.--cf. Brit. mus. cat., v. 63, col. 1585.
As you pointed out, the reference to "Das Verhalten ..." obviously is a mistake.
Maybe it has been translated from another work in this "collection of Prussian army regulations", the whole mixed lot having been named after its first item, which happend to be "Das Verhalten ..." ?
I don't know from which work Rottenburg's regulations of 1798 were translated, or whether the introduction by Fawcett means Rottenburg himself is this "German officer of distinction".
As the original was "written by a German officer of distinction", which means the author was known, it doesn't seem to have been an official regulation, as these official regulations were usually written by a commission of several officers. I don't know any Prussian regulation of the 18th century which was written especially for units equipped with rifles, but of course this doesn't mean there was none.
That the German original (if it exists) is found in this alleged "collection of Prussian army regulations", needn't surprise us, as this description of the mixed lot is not very exact if it a also contains "Das Verhalten ..."