My apologies for the delay in anyone getting back to you on this. Admin have been very good to point me towards this query however I have delayed on my response due to heavy workload up to this time. The reason none of the usual volunteers one else has possibly replied is that you really need someone from that particular area or at least Donegal to help you and it looks like your ancestor would have emigrated at a time when there very little records available apart from the Marriage record you have already. I am a volunteer from Donegal however I am living nowhere near this but I will see what I can do.
I would like to see if there is some way we can put together more information on your family and their connection to that location in Donegal. After this, we could try and advertise this locally in that community and see what feedback it may produce.
Let me know if you get this and we will progress further if you are happy, thank you for your patience.
Seamus Callaghan (Kerrykeel, North Donegal)