Hi Al
As Johnathan marries Emma Roberts in 1862 the second John you found wouldn`t really fit, I am still placing my bets on the John Smith you found who died in 1876, like I said there seems to be some resources whereby you can find out who reported the death, sadly I am not a member of Ancestry.com or any other such sight now, but if I could get that sort of information I would have thought (especially if it is Emma (his wife) or a family member who reports his death, it would go part of the way in confirming that it is "my" Johnathan.
The only second thoughts I have is if he was in Oxton for all the censuses why wasn`t he there for his death?
Like I said if I don`t get any luck from this site I may order the death certificate.