Looking for John Vaughan Surgeon of Dublin before 1841

John Vaughan, surgeon died in Sydney at the Racecourse Inn, Homebush where he had been living for 3 months prior to his death, on 29th March 1858 aged 46 years having been in Sydney for 17 years.  His death certificate states that he had a wife in Dublin where it also states that he was born, with children of marriage listed as unknown.  I can only find one record of his working in a capacity as a surgeon which was for 18 months at St Patricks Total Abstinence Benefit, where he gave his services as a surgeon to members who paid a small subscription.  He also worked as the printer and publisher 'for the proprietors' of Bell's Life in Sydney and Sporting Reviewer for about 18 months and at the end of his tenure the paper printed a statement that he was no longer connected with them and that he was better known as Dr John Vaughan.  He features in letters printed in various Sydney papers on various subjects including Irish home rule and his testimony in a libel case was detailed in Bell's Life in Sydney and Sporting Reviewer, after he had left the paper, when the implication that he was intemperate was strenuously denied by him. I also have shipping records which indicate that he took voyages up and down the coast suggesting that he might have had independent income. He is not listed in online historical list of doctors in Sydney, which is puzzling. I cannot find a will in online records. I have not searched Trinity College Dublin's listings of surgeons attending there but he was Catholic and I understand this may have excluded him.

Was he a "remittance man" or a runaway from an unhappy marriage and what qualifications did he have as a surgeon?  

I am trying to establish if this man was the father of my great grandfather, born in Sydney to parents John Vaughan and Mary White according to baptismal records.  As the parents were not married and my great grandfather was brought up by another man, at least from aged 7, I do not have any further details beyond the fact that they came to Australia in 1841 when there was an influx of bounty and unassisted migrants to the colony.  Mary White was a bounty immigrant, aged 18, who arrived in Sydney in August 1841 on the ship John Renwick, almost exactly 12 months before her son was born. According to the shipping records, she was a illiterate nursemaid from Galway, daughter of weavers but her death certificate in 1860 stated that she was from Dublin.  This is possibly because the ship came from Dublin as official records of the time include what ship a person came to the colony on.  Unfortunately I can find no records of Dr. John Vaughan's entry into the colony probably because he came as an intermediate passenger whose names were not listed in ship's records. But as the death certificate of 1858 stated that he had been 17 years in the colony it is possible that he came onthe same ship as Mary as family believed both parents did.  However if this is the case he did not admit to being a surgeon as newspaper listing of shipping arrivals stated that the surgeon on board died on the voyage and as there was no other doctor on board the captain filled the role.  

I have not found this man on familysearch to date. Was he an imposter? 

Can anyone throw any light on this man?