Hmmm all the way up to the little mark should turn everything on, when it is set to just "on" the rear control wheel should be disabled? (Sorry for not being clearer). If it's not that I don't know
Yeh, when set to 'On' you can't use the wheel for exposure adjustments etc. (but you can still use it to scroll through pictures obviously). The - is for creative mode basically.
I think the idea is to prevent accidental over / under exposure maybe