So, onto pics and discoveries. First, the gutted room:
Now, below you'll see a quick drawing of my current first floor layout. The front door is central and the only way to get to the kitchen is to pass through the dining room.
But, when the room is gutted, first I ended up with an opening just inside the parlor to the side of the entry door. Newish studs. Sill cut down a bit. So this makes it pretty certain that my original hunch was correct...this house originally had two front doors, one that went into the Parlor and one into the dining room. My first clue came when ripping apart the entryway at the base of the stairs, because the sill there at the current door opening has two mortises where studs originally were, and a hole and foot marks from a steam radiator and piping. So I guess in Victorian fashion, when entertaining, guests would have come in through the door that led directly into the parlor. When food was being served they would then walk through doors that closed the rooms off from each other, pass the stairs to the second floor, and then into the dining room. I can tell another entry door had existed in the same position into the dining room...hollow sounding sheetrock covering the spot when the rest of the room is plaster.
Also, at the back of the parlor, you can see where a door or passage had existed at one time. It got patched up rather slapdash with non-continuous studs. On the other side of this patch is the landing for the basement stairs. So I believe when the time comes, I will find the same patch where a passage existed in the dining room as well, meaning you could basically walk around the house in a circle if you wanted. I've seen this exact layout in similar I-houses in and around my town.
So my best guess is that the first floor originally looked like this:
Never a dull moment, folks.
!