I am also searching for David Wellington Finch history.
I have found that he is buried in Mapleton Cemetary in Mapleton ON. His wife Rebecca is also there. Marker shows David Wellington b. Jun 27, 1816 d. Oct 31, 1865 and Rebecca House b. May 31m 1822 d. Aug 26, 1898.
I also know they had a son Thomas Henry 1844-1917 from his certificate of death and certificate of marriage.
Have you found any more on David Wellington?