To the OP-
It sounds like you have extensive structural issues to address, especially in that exterior wall. A book I highly recommend is
Renovating Old Houses by George Nash. It documents a lot of structural techniques that might apply. Caveat in this situation if it were me I would take the book just as a starting point to get ideas and probably want to bring in a pro.
Some more about framing methods. This is what a true balloon frame looks like for anyone interested:
First known balloon frame building was around edit 1832
1840ish. Before that everything is post and beam, though there are lots of variations in how post and beam is done. Some had no studs at all and plastered the sheathing directly, others had studs at odd intervals to support the interior wall finish. And then there are variations like plank framing that had had continuous 1-2" vertical boards mortised into the sills and plates (eliminating the bracing). Plank houses are especially tough to update as the plaster is typically applied right to the inside of the planks leaving no cavities to run wires or insulate.
After the civil war balloon framing started to spread, first popular out west, but it didn't reach New England until the late 1800s You can find post and beam houses in NE up to the 1860s and later, and even after that they would build a hybrid called a "New England braced frame" , that was a balloon frame with post and beam type Corner posts added and some knee bracing. After 1900 I think its mostly pure balloon framing and then platform framing sometime before WW2.
Ehouse, of course am no expert, but your 1817 house sounds like standard post and beam construction (both my mud sills and top plates are 6x7 beams) and the 1890 house is probably the New England hybrid frame type I described above.
Anyone who has real interest in this stuff, there is a great book called
A Building History of Norther New England that shows the evolution and has drawings of each type. Its a great resource written by the first curator of the Strawberry Banke Museum..