I can't find a surname suffix of my Polish family anywhere
That's because it isn't a "suffixed" surname. It's a Polish surname which means "heir", "successor" or "squire" (one of the meanings of "dziedzic" is 'a man of high social standing who owns and lives on an estate in a rural area, especially the chief landowner in such an area' - squire) :)
geographical region called Dziedzice
Not a geographical region, but a part of a city that used to be a village. There are also a few villages with this name in Poland.