"...Both his marriage certificates and death certificate show different ages and places of birth"
Two marriage certificates, one death certificate. We need to know what is on these documents. Do not identify people who might still be alive. What do you see for parents names, birthplace etc.
This arrival in New Zealand
Auckland Star 3 Sep 1879 p2
https://paperspast.natlib.govt.nz/newspapers/AS18790909.2.10?....COLQUHOUN family......
Online tree for Rosina Harvey COLQUHOUN m. Fred PORTER in NZ has this family in Ireland, including Ballybo, Donegal.
WW1 enlistment file ....I am seeing C of E for religion at images 9, 15, 26 and 27.
At image 25....name........ R Joseph COLQUHOUN..........