I think your Margaret might have been Mary.
The information doesn't agree too well on the censuses because most of them say the family was from Luxembourg but others say from Germany. One census says they immigrated in 1860, but it must have been about 1862 because children John, Clara, & Catharine were born by 1862 in Luxembourg, and Nicholas was born about 1863 in Iowa.
Mary's age also varies. She was 36 in 1870, 46 in 1880, but 64 in 1900 [b. Aug. 1835] & 75 in 1910. She died 26 or 27 Oct. 1911, aged 79 or 80 [cemetery & county records, age probably exaggerated]. Your birth date of 8 Aug. 1836 could be correct. What is your source for that?
The only other BENTZ burial in Emery Catholic Cemetery that I know of is a male who died in 1920 aged 86 [only the surname is listed]. That wouldn't have been Mary's husband who was born around 1820/1 [50 in 1870, 59 in 1880].
Mary had ten children and only six were living in 1900, so the others are probably buried in Iowa. There's a break between Nicholas, b. ca. 1863, Iowa, & Jacob, b. July 1869, Iowa, & another break before Suza in 1877.
--not my family