I've done much digging recently and I believe that James, s/o Thomas Mason Dungan and Nancy Mason is James Algie Dungan, but that is a guess at this point.
I did determine that my John T Dungan was s/o Joseph Hall Dungan and Sarah F McLeod (sometimes spelled McCloud). It seems that Nathan's children from Lillie Hamilton were sent to Perry County Alabama (see post 586 I think). Joseph shows up on the 1860 census there living with Jno. B. Dungan. On 28 Oct 1864 he marries S F McLeod in Perry county Alabama. By 1870 They are in Ballard County, due North of Crockett County, Tennessee where John and another child, William, have been born. This pattern of migration fits with the 1930 census that I found (when Dungan was transcribed as Duman incorrectly). In the 1870 census the Dungan family is listed immediately above a McCloud family, probably extended family of Sarah.