It's hard to believe that you could grow grain on rock. (I have a copy of that petition). There are no gravestones known for Hugh and Biddy. If there were Anglican records, I would think they may be in Sackville or Saint John, but I haven't heard of any.
Hugh was the son of William and Annie (McKinley) Alcorn. Annie was still living in 1851, but William had died at the residence of his son Andrew before that. I have seen people say that WIlliam and George Alcorn were brothers, but I haven't seen any proof of that. This place is polluted with Donegal immigrants, (McKinley's, Alcorns, Kyles, Bogles, Cairnes, etc). It was like someone took a whole village from Ireland and plunked it down in New Brunswick.