Bucktail,
That compressor will not be able to keep up with the 9 CFM requirements of the impact wrench for more that a couple of seconds. More importantly, if your bush hog is like mine you access the nuts for the blades from the top through an access port provided just for that. If the splined bolt is spinning in the arm no amount of torque will get the nut off. You will have to either come up with a way to stop the spinning or cut the whole bolt off.
I used a breaker bar with an 8 foot cheater to get mine off. Sounds like yours are like mine based on the size of the socket needed.
Good luck and may the orange force be with you.