If you had given us John's name (McFall) and the place of marriage (Rathlin) at the beginning we would have saved a bit of time searching for him.
Much of Ulster, especially North Antrim, was settled to Scottish families and it's not uncommon for them to say they came from 'Scotland' or 'Ayrshire', etc. My grandmother's ancestors came from Isle of Skye to Co. Londonderry and after several generations our branch of the family went to Canada- later generations always said they were from Skye and it was only when I read notes in a family Bible that I was able to trace them in Ireland.
Have you found John in Scottish census records (1871, 1881, 1891)? what's listed as John's place of birth- Ireland or Scotland?