Wow. Thank you so much Cortman.
For 1 and 2 I altered
by putting in:
sudo leafpad /etc/xdg/lxsession/Lubuntu/autostart
xkbset exp -bell -sticky -twokey -latchlock -accessx -feedback -stickybeep -led 9999
xkbset bell sticky -twokey latchlock feedback led stickybeep
This worked fine!
But for 3 (Super Key to remapped as a "page down" key), I couldn't understand "man xmodmap"
I found when I do
one of the lines which might have something to do with "page down" reads
keycode 88 = KP_Down KP_2 KP_Down KP_2