I would be interested if you have anything definite about Fr George ceasing to be exarch in 1953.
I am having difficulty obtaining reliable information on this point. It may take a couple of months to gather enough to come to a reliable conclusion.
I suspect however, that there may have been for a while two exarchs in Australia at the same time, one in Melbourne (Fr George Haydar), and one in Sydney, with duties centred at the parishes they served, with the only real boundary being the NSW/Vic border. But even that border was iffy, since both went to Albury on the border at different times according to ability.
Generally speaking, Antiochian Orthodox priests tried to be agreeable and not worry too much about formalities. They would make mutual decisions on what was sensible at the time, rather than on hard and fast rules, or lines drawn on maps.