Regarding old damp courses,2 layers of slate would work fine,with the 2nd layer over lapping the joints of the first,or 2 courses of Staffordshire blue bricks.
Yes, I think they either didn't care, or didn't understand about how it should be done. Same with the fire wall. Not sure when the regulations came in round our way, and if they were more used to dealing with flint build, I don't know if those have damp courses as the flint is impermeable anyway.
I think different places brought in building regulations at different times. In London even stricter regulations about non-flammable materials on the outside of buildings, such as door and window lintels were brought in after the Great Fire, but suspect in small towns and rural areas, the regulations were far more lax for far longer.