I believe this may be him w/parents in 1850. The birth year is way off. But his birth year is off by about 10-15 yrs. in all of his records. If it is in deed him, either his gravestone is wrong or all of his other records are wrong.
If you search for him with a later birth year (1824-1831), you should find all of his census records. He moved around a bit. And it appears he was married to a Judy Evans before Susan and has older children.
I will post his 1850 and 1870 census records.
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MZ4V-6PY : 9 November 2014), John Reams in household of George Reams, Winneshiek county, Winneshiek, Iowa, United States; citing family 23, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).
"United States Census, 1870," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M4Z6-CBX : 17 October 2014), J R Reams, Dakota Territory, United States; citing p. 11, family 93, NARA microfilm publication M593 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 545,617.