As I tried to explain before: your ancestor was a so-called "Schutzangehoeriger" - a citizen of an annexed territory who was neither considered a foreigner nor a German. Such people were usually put in either category 3 or 4, unless they were Jewish. Since you've said that some of your ancestors considered themselves Prussian-Germans, my assumption is that a German female from that side of your family married a Polish man with the surname Mackowiak. If this is true, Thadeus should have been in Category III of the Volkliste. For details, see #24 above.
HTH
HTH