There very may well be another Mason Calderwood "out there" but I agree with your idea about the "off target" info. It's good you have the SSDI and Bible link too.
Have you noticed that Scott County, Iowa on line info has a fair amount of Calderwood's?
Henry Mason and brother John Alfred sure got around the country alot. Another brother, James appears to have been in Nebraska while John was (1890 farmers list). And brother Alexander was in Illinois when John and Susan Campbell were married in 1880.