My family of Allains also comes from Bouctouche, but I am not able to help you with your Damien. I have a Damien, but no son Octave.
I don't know if you are aware, but the original Allain in Canada was a Louis Allain,born ca 1651, who arrived there from La Rochelle (most likely)France ca 1685. All Acadian Allains are descended from him. He had a son and a daughter: Pierre-Louis born 1690 or 91 in Port Royal - died Brest, France ca 1744, and Marguerite born ca 1693.
Pierre-Louis had sons: Louis bn 1722, Pierre bn 1723, Antoine-Joseph or Joseph-Antoine bn 1729 (died at age 17), Benjamin bn 1732, Jean-Baptiste bn 1741; and daughters: Marie Elisabeth, Adeline-Marguerite, Marie-Anne, Marie-Magdaleine, Marie-Josphe, Marie, Marie-Francoise.
So, you will find any Allains are descended from one of these three generations. Good luck in your searches.