To flatten the lockwasher - you need not only a screwdriver but a small hammer, to put it back into place. I bought three or four new washer, and I plan to use only one of the tabs each time, so the same washer is good for four or five uses.
Regarding the way to loosen the nut, I hope my picture speaks for itself. Just make sure you don't exert force on the ends of the clutch basket tabs, but closer to the basket body. If you have a strap -like the ones used to tie bikes on trailers- you can use it also to keep it from spinning. I've used that on an alternator rotor and it worked, as I couldn't think of anything else to keep it from turning.