All the tabs should be level to release the nut. When one is bent up it locks the nut in place. Carefully bend it down. Then you should be able to unscrew that nut.
It would be a good idea to put a good wrapping of tape or some other padding around the threads at the top of the pulsator shaft, just to be sure the threads don't get damaged while you are working on the mechanism!
Those 2 on the left were level and so were the rest. I bent them down with a screwdriver and hammer. They face the bottom of the tub now. I think I did something wrong.
The five o' clock position is bent up to lock the nut on. It needs to be brought down to level. The 7 and 9 o'clock tabs were o.k. to begin with so you will need to bend them back to where they were at a level position.