I am also researching the Erwin / Irwin name and I have many of the same family members identified as possible links
They are all in the Ballybay, Monaghan, Ireland vicinity - I am going to export all the names from familysearch.org in that area and map them all together
I have a John Erwin born 1860 - who was a colporteur - seller of Bibles - Methodist in religion. They lived in Ballymena at the end of their life - but lived in Boyle and Enniskillen as well. they had 13 children. Hugh, James, Elizabeth, Edward, Margaret, William, John, Samuel, Joseph, George and Thomas Alexander (the other two died at birth)
I am trying to establish if the Ballybay folks are Johns ancestors. They all moved to the USA or canada except for 2 - one died and the other went to Scotland