I just ran across your message from a couple of years ago and while I can't answer your questions I have family lines back to St Sophie d'Hallifax in Megantic county as well. Much of the church records have been microfilmed by the Mormons and you can order (loan or to buy) the microfilm at any of the reading rooms set up for using it. I have actual copies of some of the marriage and birth/death entries of the Lamberts and Bouthets. If you have lost lines from there it seems that many migrated over the boarder into the US in New Hampshire (mine went to Berlin and then to Portland Maine). You can reach me at the listed email or quicker via Fireflya54@aol.com
(I am on this screen name at least daily). Please make sure you put genealogy in the subjest line.