Exhaust removal - confused, How do I get this sucker off? Options

[ThePaintedMan]

Hello all,
I've been meaning to look for an exhaust leak at the head for some time. I ordered new copper rings, but before I can install them, I need your advice on how to get the exhaust off. As you can see in pictures, the headers have been so boogered up, that it is impossible to fit a socket on some of the barrel nuts. Its like the whole thing has been bent sideways, which means the header is butted up against the barrel nut. One of them in particular is really an issue because for whatever reason I cannot reach the top of the stud. The barrel nut is so far down along the thread that there is nothing sticking out far enough to get a socket on. To make matters worse, while tinkering with it, I backed one of the barrel nuts off only to find the stud pulled completely out. Is it possible to insert a helicoil with the engine in the car once I get the exhaust off? Thanks for the help!