I'm confused....you 1st state Henry/Harry is great grandpa, then you say he is grandpa.
If you're unable to obtain an obit [Detroit Public Library], I might suggest you obtain obits for his siblings....they may mention Henry/Harry.It would narrow down the timeframe for his death. Charles W d 10-11-1931 Dayton, Montgomery Co OH Chester Franklin d 1-13-1926 Detroit James d 9-6-1925 Tucson, Pima AZ
OH Deaths states John M d Champaign Co, not Clark Co.
I'm curious as to why you don't have Harry's sisters, Mary WILDERMUTH; Laura P WING, listed on findagrave....even without deathdates it might help someone else with their research.