Hi,
I think I have narrowed down Edwin's death in Chicago in that whilst the 1865 census does not show names, there is an entry for Ed Watson and next door is Sarah's father and family Wm Linton. This situation also applied in the 1860 census. So it seems he was alive in July 1865
I wondered if it was possible that the City directories has Edwin listed between 1865 and 1870?
Alan