I know you posted this several years ago, and I don't really have any answers for you, but I just wanted to say if there is any chance you see this, I also have lines with this surname. I use FUESZ as that is the most common/eldest spelling I've seen on vital records for my lines. Conrad (1804-1876) and Sophia (?) started a line in Buffalo, New York; I've seen many of these spellings, but not all. It seems to have become FEESZ in later years.