Nelson Chapman is also found in Mill Creek Twsp 1860 census Morgan Co Mo Dwelling 735. Note that James C Puckett was a neighbor of the Chapman's. (see below) Nelson (nat: KY, 23 y/o) is in the home of an apparent brother Charles Chapman. The two enumerations were taken several weeks apart between Moniteau and Morgan Co. The Captain William Chapman of Schnabels is likely the William Chapman listed in Moniteau Co 1860 census. (age and nativity match) The relationship between William and Nelson is undoubtably close but I can't make it father-son given current known info.
His occupation is that of cooper ie barrel maker.