Much of the records that I sent you were speculative. As you know somehow the records don't add up regarding what happened to husband of (Mary) Ann Sells. Something doesn't seem quite right. The only John Sells that seems to possibly fit was from the same family (father was a plasterer) but again no death record or reference in newspaper.
Another speculation: I have seen wives listed in census records (sometimes in 2 or more census records for the same person) as widowed when they were separated from their husbands.
Checked for any Sells that was listed in obits in Phila Inquirer during that time and no possible matches. Did not see any George Sells listed as cashier (or clerk) in Phila city directories during that time either. Will keep checking for some kind of conclusive evidence.