[s5uewf]

What is your ultimate goal in removing the exhaust?

If you are going to throw away the current muffler, one option might be to cut through the exhaust pipe and remove the cat/test tube/muffler. then you get a straight shot at the bolt.

I am able to fit a crows foot in there with the square connection hole toward the engine, and then connect a 3/8 small breaker bar or small socket to it and turn it a few clicks at a time and then reset and turn again.

If you are now dealing with rounded nut you may have to cut. if you cannot get a dremel in there, then a hacksaw blade with tape over half of it so you can hold it in your hand might work. Or you might be able to get a torch on it though that would be tough.