The big nut (30mm maybe) holds the axle into the hub. It has nothing to do with the wheel studs. If you remove it, you still won't be able to do anything aside from pressing the hub out of the knuckle if you take it ALL off the car.
If you are trying to replace a stud, knock it loose with a hammer and rotate the hub until it find a 'happy place' and falls out the back. To replace it slide it in at that piont, stack up some washers on the new stud and use a regular nut to 'suck it in' to the hub. Not an air gun- you need steady torque, not a hammering effect. Pull it right up to about the head seats on the flange. May take about 80 ft lbs or so to do it, just don't lean into it for all you're worth or you'll be doing it again....
Leave that big nut alone.
