With the help of those other researchers, it looks like you are almost there in solving the puzzle of your Abair/Mayo ancestors.
In the mid-1800s, there was a huge migration out of Quebec, as they looked for work in New York and the New England states.My French-Canadian grandfather was born in Rhode Island, for example.
In many cases, their surnames started being recorded phonetically, in other words, written in English the way they "sounded".For example, Côté became "Cody".
In your family, Hébert [pronounced ay-bair, without sounding the "h" or the "t"] was recorded as Abair, Abare, Abear,...So, in answer to when that happened, it was probably the first time the family had to have their name written down in some formal document, like a census, birth or marriage.
The same with Mayo.The two common French-Candian names that could have derived from are Maheu [ma-ø] or Mailloux [ma-you].The "L" is not pronounced, same as the double-L in Spanish.
In Carolyn's post, she discovered that Théo recorded his mother's name at his wedding as "Mahen".Almost for sure, the registrar wrote "Maheu".But now, this recent researcher seems to have found the "Mailloux" spelling too.
So, keep plugging away.You will probably find your answer in some little village in the Richelieu valley, just a few miles away from your ancestral towns in Vermont and up-state New York.I know there were several Hébert families in St-Jean, St-Mathias, Chambly, etc...
Yes, there were several Acadian families who made it back to Canada after the expulsions.Many of them settled in the Richelieu valley.Some of my Acadian ancestors landed in St-Antoine-sur-Richelieu.They also founded a town nearby; they named it L'Acadie.
Just a few more tips:always keep open the possibility that the name of your subject is written differently in French.So, Lewis Mitchell could turn out to be Louis Michel. Angeline could have been "Angélique".Josephine could have been "Marie-Josèphe".Harriet < "Henriette".
Finally, you could access another set of great researchers if you post your message on the "Quebec" forum.On the Canada page, see the hyperlink up to the right that says "Regions for this Country". You will find it in there.