Murray family of Moreau, New York

I have been researching this amazingly illusive family since 1968.  The furthest back I have is Iram Murry who appears out of no where about 1790.  His wife was Lydia according to the land records of both Saratoga and Washington Counties.  He lived in the Northumberland (Moreau) area outside of Fort Edward from 1790-1814,  Using genealogy bank and Old Fulton Postcards I find the last surviving (batchelor) son whose estate was probated in 1875 in Saratoga County, NY.  I cannot find out what became of Iram (1750) or his wife Lydia after 1814 when I find him in a census return in Adolphustown, Ontario, Canada.  That is the last record I find.  No land, court, burial, cemetery etc etc.  I trace his kids all around and nothing indicates he was with them.  Can anyone point me in the right direction?

Nancy