Jane's tombstone at Mansfield City Cemetery says "Jane E. wife of Nathan Amsbaugh died 10/9/1832 aged 26y6m5d"
David R Amsbaugh was born 9/21/1832 per his Richland County Death Record which says he died 10/1/1912 aged 80y10d. His tombstone at Windsor-Woodhouse Cemetery also says he was born 1832. She apparently died 19days after his birth, probably as a result of birthing complications.
David Amsbaugh, age 18, is living with his grandfather, Valentine Amsbaugh, in the 1850 census.
None of Nathan's siblings could be David's father other than possibly George, who married Leah, since they were too young in 1832 or weren't yet married.
David fits with Nathan and Jane by elimination and the coincidence of the birth/death dates of David and Jane, and his living with grandpa 18 years later.