All your talk of remodeling projects and dreams. . . That is what DH and I have done all of our married life. We purchase old homes and gut them from the inside out, repair, and the tear off everything from the outside in (to our repairs) and redo the windows, siding, etc.
I am so used to living amid construction tear out and replace. Dad did much the same when I was younger, buying, living in and fixing up 860, 911, 953, 1725, 748, 848, and 947 before I married and we continued with the fixing -- not so much the living in -- once this house was built.
DH had done much the same type of repair work with his father before 'us'. I have seen (and helped) level some pretty un-level floors. All the older houses seemed to sag from the limestone foundation walls to the middle of the house. Lots of beams added to basements, lots of shims added to everything else.
The monster DS has is a fine example of a lack of plumb bobs and squares in old buildings. Still, you can do anything with plastic pipe and wood is very forgiving. The first house DH and I bought was a two apartment. We moved into the upstairs with 'bedrooms' for the kitchen, dining room, bathroom, etc and a hallway down the middle. We got rid of the hallway entirely, moved the kitchen into a bedroom, put the bathroom fixtures and door in another wall, and opened the living room to a living room/dining room open space. You would never recognize it as the same place. Once it was done, we moved downstairs and rented out the upper.
It is easier to move walls about upstairs than down. Especially since there was a wall of oak cupboards between the kitchen and the dining room, but we put our mark on the downstairs apartment (always need new kitchens and bathrooms) before we bought the land and started building our forever home.
Steve, if DH and I were younger. . . . DH is a miracle worker when it comes to fixing up old houses.