I think that this is the story to date - James marries Lucinda Maria in Ballarat and she dies there in 1861 - he sells up in 1862 and moves to Adelaide possibly even "picking up " or marrying Janet ML ? on the way. When Janet dies very suddenly he has a "UGH" moment and puts the wrong name on the death notice.However by the time the monument is to be erected he realises his mistake and puts on the correct name.
James lived all his life in SA in the Bowden Brompton Carrondown and Hindmarsh area - all of which are within a very small radius at that time and this is where Martha, his new wife, and he raise all their children including my grandfather. She dies in 1886 and with a still young family he marries another widow, Fanny Butler to help look after the kids.
I think I will have to be happy with this scenario at least for the present.