I have had a pneumatic impact wrench in my toolbox for many decades but I can't recall using it for the last 20 years. I think I would grab it, though, if I encountered what you are dealing with.
Good luck.
Edit: Also, I'd probably mount the NDS crank in a vise with soft jaws instead of lashing it to a stay. Probably wouldn't happen; however I'd be concerned about bending the stay.