5.45 How can I force Emacs to scroll only one line when I move past the bottom of the screen?

Customize the scroll-conservatively variable with M-x customize-variable RET scroll-conservatively RET and set it to a large value like, say, 10000. For an explanation of what this means, see Auto Scrolling in The GNU Emacs Manual.

Alternatively, use the following Lisp form in your .emacs:

(setq scroll-conservatively most-positive-fixnum)