Re: Lathe and plaster walls
The pictures came through so small that can't tell if I'm seeing old wallpaper residue, old wallpaper paste, or drywall paper. If your walls are plaster, not drywall, they would have one of these surfaces: 1) A smooth white coat of plaster. This is waterproof and any amount of scrubbing isn't going to bother it, and you can keep scrubbing with wallpaper remover until the surface is clean and ready to paint.
2) a "float finish " or "sand finish" plaster. This is a coarser texture than in 1), and the surface was left intentionally sandy and rough. If wallpapered over, it's harder to get the paste off, but still, it is waterproof and scrubbable, tho' you will probably loosen some of the sand, but won't remove all of it.
If there is some other condition, it is not original. There was no drywall in 1903.
Remove not the ancient landmark, which your fathers have set.