It is a noble cause to inform family members about the wartime captivity of their ancestors.
However, it will be difficult. If none of the former prisoners later became a public figure, there will be hardly any publicly viewable information about them. Genealogical databases are not relevant in Germany for the period of interest. Civil status registers are ...
Yes. Mönchengladbach was called München-Gladbach (shortened to M.-Gladbach) between 1888 and 1929, then Gladbach-Rheydt, then München Gladbach without the hyphen, then Mönchen Gladbach. Only in 1960 did they switch to their current name.
( German source, Britannica also reports the old München-Gladbach name. )