Secondly: how do I turn off the smart-scrolling *completely* everywhere.
I know how to swap its behaviour from one form of scrolling to another,
but I never want the Action Key to trigger scrolling, and I can't see a
way in the manual to do this.
There are two variables that determine what happens when the Action or Assist keys are pressed at the end of the line:
action-key-eol-function and assist-key-eol-function
So add these two lines to make these do nothing:
(setq action-key-eol-function #'end-of-line)