Oh Hooray that you found some info on your family.That is always exciting. The last name of Thomas very well might be Bernard/Barnard/Barney/Bouchard etc.I have seen all of these spellings among the Indian folks of New England. As a matter of fact, a family of "Barney's" who one of their children was listed as "Indian" on the 1870 census, was living next door to my 3rd grt. grandfather who was the Indian doctor. One of the Barney girls was living with him and was enumerated as Indian and born in Canada.The others of the Barney family said they were from NH and Canada. I suspect they were Bernard's however and most likely all of them were Indian, but as many of the New England Indians do, they could easily pass for whites.
As for a reservation in that area that you mentioned, I don't know. There were no doubt probably Indian camps.There were a lot of Abenaki's, Seneca's and Mohawks in that area as well as others. Some went over to the Lake George area of up state NY too and some back into Canada and other places. Check to see if there were any lumber mills/saw mills/ or woolen or cotton mills in those areas.Many of the Indian families worked in the mills in those days (around the 1830's on up) as mine did too in Maine. Good Luck to you on your research, sounds like you are on your way.