The brightness key issue eventually went away for me. I was able to resolve (mostly) the mouse-after-suspend issue. I added the following to /etc/pm/sleep.d/00_usercustom:
Code:
    modprobe -r bcm5974 
    modprobe bcm5974
The whole contents of that came from one of the postinstall scripts in https://help.ubuntu.com/community/MacBookAir4-2