J.

Sorry to hear of the bad back. These cheap impact wrenches are not a
solution to lug nuts. As mm suggests, get a breaker bar and the correct
socket, stand on the breaker bar, and bounce up and down. I'm pretty light
and this always works. Once you've moved the lugs use a ratchet to get them
off. The danger to your back will be in putting the tire in the trunk.

Dave M.