Do you have information on the James you identify as a brother of Samuel McCulloch? I have a James McCulloch (same spelling) who appeared in Christian Co. KY by 1811. Born in Ireland, ca. 1770-1780. Married a Jane, last name unknown, born in PA. Died about 1822 in Christian Co. This James McCulloch had still equipment in his estate inventory, also a few medical books. His grandson, John Wellington McCulloch, had a distillery business (Green River Whiskey) in Owensboro KY.
James had some unusual names for a couple of his sons -- Hamilton (Rowan?) McCulloch and Hannibal McCulloch.
Since James's wife was born in PA, I am wondering if there is any connection with your McCulloch family. What is the history of McCulloch Mills?