McGowan and maybe Quinn, probably in Sligo

My maternal gt grandfather Mick (Michael) McGowan is a brick wall that Ive been trying to break through for years. He was born around 1865 (evidenced in various records). In the 1911 English census it says he was born in Sligo. the 1911 says Galway. Additional circumstantial evidence that it may have been Sligo comes from the very unusual given name Phelim / Phelam (and other variants) which he gave to 3 of his boys who all died very young. From what I can glean, this name is far more common in Sligo and Mayo than anywhere else in Ireland.

Another possible clue about Mick's past is that in both 1901 and 1911 he's living under the assumed name of Quinn - best not to ask, he was a fairly difficult character and a bit itinerant, I assume he was in trouble with the law, but I dont have any hard evidence of that. My experience of assumed names is that there's often a link somewhere, a reason why the assumed name was chosen.

On his marriage certificate in 1894 he said his father was called John, and that he was a farmer. So thats the only hard evidence we have about his birth family.

Ive done a deal of searching over time, and my best current guess is that his father may have been Owen McGowan and his mother Mary Quinn, which fits with a baptism for a Michael McGowan in Cloonerco, Ahamlish parish, in 1866. There would also have been a sister Bridget born 1869 in the same place, and probably died there the same year. Ive also found a Griffiths record for Owen McGowan in Ahamlish parish in 1858 which could be him.

Any help or further thoughts anyone has would be much appreciated.