Hey Keith, I might be able to help you go back!
I too have ancestors in New Brunswick and Nova Scotia, and I have found that the waves of immigration very quickly moved west. This means that a Smith who was born in New Brunswick in the 1840's was likely related in some way to the earlier immigrants, and I would guess that applies to the Balmains too.
So following that train of thought, the first Balmain in NB seems to have been William, a Scot who married Margaret Niven in Glasgow in 1772. Here is the marriage cert: (
https://familysearch.org/ark:/61903/1:1:XTBH-R6R)
I'm reading that William and Margaret settled in New York and then came to New Brunswick as Loyalists with their family in 1783: Here is the Loyalist Directory listing.
http://www.uelac.org/Loyalist-Info/detail.php?letter=b&line=62; and here he is in Sabine:
https://archive.org/stream/americanloyalis00sabigoog#page/n156/mode/2up
The UELAC directory shows a list of children, including three sons who all seem to be born before 1790. If I was looking for Mary Jane, I would start with William and Margaret's three sons and see if I could work forward to find their descendants. Maybe the people who worked on this listing could give you some threads to pull.
I also found a possible start of a WikiTree profile for William. Its not sourced, but I wonder if a man who is born and died the same years as the one in the directory listing may be intended for him:
https://www.wikitree.com/wiki/Balmain-47 This might give you a line of enquiry if his decendants don't lead you to Mary Jane. Its possible that one or more of the possible brothers listed here may have joined him in New Brunswick later on.
I'd be surprised if the apple fell farther than that.
Happy Hunting!
