I have been researching your ancestor, David Downes.
I found a 1880 Federal census and it states he was a ship carpenter and lived in Detroit born 1847 and married to Georgina Root born 1856 (parents -Legrauge & Isabelle Root)per1870 US Fed Census. I found a David Downes born 1835 and died July 29, 1895 with New York Records. The Detroit City Directory 1896 states Georgina and David lived at 83- 2nd Ave, Detroit, also states at in 1900 Georgina lived at 81 2nd Ave Detroit. also I find a 1890 City Directory shows Georgina as a widow of David and lived at 125 -18th St in 1890 and 1891. I don't know if this is the correct David Downes but it may give you info to follow up on if you haven't already. If you haven't found his grave site you may want to call Elmwood Cemetery in Detroit and Woodmere. They are some of the oldest cemeteries in Detroit.
Mary Ann, born and raised in Detroit. P.S. I'm still looking for my great great grandfather and mother for their burial site after looking for 2.5 years.