Sorry...no information on the Susan Conrad you mention.
Now, how much more confusing can this get what with the Dodge family insisting on naming their children with many of the same names.
My Rev. Josiah Dodge 1762-1800 had a John Dodge born 26 January 1787 in Canterbury, Ct. and dying 18 May 1873 in Abingdon, Knox County, Illinois.He married Theodocia Dodge 01 August 1811 in Hardin County, Kentucky.The surety was his uncle, Richard Winchester who had married Josiah Rogers' sister, Lydia Dodge.
Rev. Josiah Dodge had a daughter named Theodocia who was born after 1796 in Hardin County, Ky. and died 02 September 1856 in Warren County, Illinois.She married 10 December 1810 James McDonald.
According to the Woodward 1904 book "Dodge Genealogy",at that time John Dodge, Josiah's brother, had no known descendants.
HISTORY OF THE BAPTISTS IN ILLINOIS by Edward Brand...page 24 mentions 1794 "Elder Josiah Dodge from Kentucky was on a visit to his brother, Dr. Israel Dodge, of St. Genevieve, Missouri."(No mention of his brother, John Dodge).It mentions Dr. Israel Dodge was the father of Henry Dodge, in later years Governor of Wisconsin.
Will Book B, page 157 lists Division of Land to heirs of Josiah Rogers Dodge 19 February 1814 and Israel Dodge is listed along with other chidren.
Unfortunately, I have nothing further on this Israel Dodge.
However, if your letter states that "his father's name was Israel Dodge, son of John Dodge born in Ct.and of Kaskaskia, Illinois and St. Genvieve, Mo. fame" then Rev. Josiah Dodge would have been his uncle....