Last night I tried the "sandwich the wheel between 2 pieces of wood" and tried the tool (bent it), and then tried a punch and hammer making rotational force via one of the holes. No dice. It is supernaturally tight.
Um...not the wheel
...ya lock the wheel with the "Shaft Lock button"
I was thinkin' to straighten out the bent up tool
...& then, "sandwich" the handle of the tool, in between (2) pieces of ~1" x 12" steel ("AKA new & improved handles)
* Put grinder on work bench (don't try hold it "up in the air") use the bench top
...& it will help hold the tool, as you apply pressure/leverage
Then, push in the "Shaft Lock Button" to lock the shaft (& wheel)
...& use the tool to turn the retaining nut counterclockwise
** Try & position the wrench so that you're pushing downwards, on the wrench, toward the bench top
Also, the same style of (2) pin wrench's, for other grinders, will work too
...even if the pins are spaced apart differently
Just insert (1) of the pins, into the retaining nut
...& the other pin up against, the outside edge of the nut
*** Sometimes even applies additional leverage
Hope ya get 'er off