The post summarizes problems in using Screen in Mac's terminal when you have the following in your .zshrc
if [[ $STY = '' ]] then screen -xR; fi
I usually solve the ctrl-a problem by setting my escape character to ctrl-z (which you generally don't need to use as often when you're running screen, since instead of backgrounding a process, you can just start up a new screen). In my .screenrc
:
escape ^Zz
Scrolling using the touchpad just isn't going to work; screen is acting as a terminal emulator inside a terminal emulator, and it's just not possible for screen to switch the scrollback buffer in Terminal.app whenever you switch between screens. You're going to have to use screen's scrollback features. See this article for some tips on using screen's scrollback features.