O'Brien, Archer, Needham in Fethard, Tipperary

Like so many Americans, I am trying to establish my Irish ancestry and the leap across the pond that brought my ancestors to North America.

Here is what I know for certain:

My gg grandparents were John O'Brien and his wife Ann(e) Archer.  By 1844 they were located in Albany, New York and had a son, Patrick Henry O'Brien, the older brother of my g grandfather.  I do not *know* where they came from in Ireland or precisely when.  I do know that one paternal DNA test associated my O'Brien line with Miltown Malbay in County Clare.

Here's what I believe, and would greatly appreciate any advice to further confirm:

1.  There is a record of a marriage between an Ann Archer and a John "Breen" at Fethard, Tipperary, 29 September,1829.  I believe these are lkely to be my ancestors.

https://search.ancestry.com/cgi-bin/sse.dll?indiv=1&dbid=61039&h=8837570&ssrc=pt&tid=42874425&pid=19848353094&usePUB=true

2.  There is a birth record at the Cashel (Tippeary) for a Mary O'Brien born to John O'Brien and Ann Archer on 7 September, 1834, and they lived in Green.  I suspect, but cannot confirm, that these are my ancestors.

https://search.ancestry.com/cgi-bin/sse.dll?indiv=1&dbid=61039&h=4935990&ssrc=pt&tid=42874425&pid=270145849837&usePUB=true

3.  There is a baptism record for John O'Brien at Fethard, Tipperary on Jan 25, 1812.  I suspect this is the John "Breen" in the above marriage record.  Mother's first name is Margaret, father is John O'Brien.

https://search.ancestry.com/cgi-bin/sse.dll?indiv=1&dbid=61039&h=4982842&ssrc=pt&tid=42874425&pid=19848353072&usePUB=true

4.  There is a baptism record for an Ann Archer at Fethard, Tipperary on 6 May 1814, parents being James Archer and Francisca Needham.

https://search.ancestry.com/cgi-bin/sse.dll?indiv=1&dbid=61039&h=4983229&ssrc=pt&tid=42874425&pid=19848353094&usePUB=true

My questions:

1.  Am I making too great a leap to assume the marriage of a John "Breen" to an Ann Archer is likely to be John O'Brien, and that this couple could be my ancestors? It seems that while John O'Briens are ubiquitous, Ann Archers are not so much in Ireland.

2. I can find no parish records pointing to the same Archer family nor to the same O'Brien family in Fethard.  Were people transitory at that time?  I rather had the idea they tended to stay in one place.  Or might the Archer family have been Church of Ireland and hence no Catholic records?

3.  Was there any known emigration effort from that specific area that might have inclined this couple to travel to North America in the range of 1834-1843 (and I might be able to narrow that to 1841).  I am aware of the general use of lumber ships to take people to NA, and specifically to Canada.  Since my ancestors ended up in Albany, I am guessing they entered through Canada.  My speculation is that they left through Limerick. But I wonder if there was any particular local impetus to leave the Fethard/Green area in the range of 1834-5 to 1841-3.

4.  I suspect the only way I could confim these are my ancestors would be via DNA match to other descendants still in Ireland.  Any other suggestions?

Thank you for your patience with this lengthy message.  This has been a 15 year quest, and I sense I am close, but perhaps more experienced genealogists would suggest I am leaping to a conclusion here.  Any and all advice would be greatly appreciated.

Thanks,

Caine O'Brien