The URL for your website does not work. Could you please post which parents you have concluded are correct and the notary reference for the contract? PRDH does not identify a marriage contract for the 1724 marriage and it would be very interesting to know what has been found that they did not find.
PRDH does show Marie Madeleine Poulin (Jean & Marie Gagne) married Francois Xavier Thibault (Francois Thibault & Marie Anne Dupres dit Despres) approximately 1724. The parents of Jean Poulin are identified as Jean Poulin and Louise Pare (certificate #28345). The parents of Marie Gagne are identified as Louis Gagne and Marie Gagnon (certificate #30209). The marriage contract for Jean Poulin & Marie Gagne is # 95017 and the notary is Etienne Jacob.
I am also wondering what is the source that shows the Rimouski couple of Jean Poulin (Jean & Anne Robin) and Marie Gagne dit Belavance (Alexis & Marie Catherine Cloutier) had a daughter named Madeleine. I find 11 Madeleine Poulins born after 1726 (their marriage) and they are not the parents of any of them according to PRDH.
I am related to Gagne, Gagnon, Poulin, and Thibault lines and am very interested in your findings.