I used a Dremel with a cutting wheel.

Remove the seat, put some duct tape or cardboard or 1/8" plywood or masonite to protect the bowl and use a sawzall with a metal blade.

I suspect only basic hand tools are what's there.

Just keep at it with the hack saw blade. Another option is grabbing it with vice grips to help turn it. You might need a screwdriver to hold it in place as you turn the remains of the wing nut.

Hi, It took me awhile to figure this out. Drain the tank, sponge out the water, Take a drill with about an 1/8 bit, drill the bolt inside as as close to center as you can. ( do not use a center punch) drill about a 1/4 deep. Then drill out the holes stepping up. 3/16 to1/4 to 5/16 that way you control the torque on the drill. If the bolt spins clamp vice grips on the bottom of the bolt. You will drill the head off the bolt and it will fall to the floor. about 5 minutes per bolt. No scratches on the toilet and no new pains in the body,
Good Luck Woodbutcher

When you get it off and get new bolts, be sure to NOT overtighten the new bolts. You can crack the tank.