Thats ALL on your mouse.. Jesus.. ha..I'd get confused.
Thing with extra functions on the mouse - it affects your aim as well - I'm an old school player with jump on right mouse and even that isn't ideal really but too used to it to get out of the habit.
For single player games I use middle mouse button as use but not for FPS games online - used to use scroll for weapon switching but now got that on the keyboard - the scroll wheel is now used to quick switch between primary weapon and fallback weapon (i.e. pistol) rather than scroll through all weapons.
Personally use 0 extra buttons.