Can't add to what JG has already said, but how terrible

that must have been a whopper of a pup, I've never seen a pup ever take 15 mins to deliver the pup must obviously have been visible, was she straining to push the rest out for 15 mins, could you not intervene to help deliver or secrete her vulva, was it a breech, or was it basically just down to the enormous size of the pup? I'm just curious as to how it took so long and caused so much damage. :-(
I'm so sorry to hear that your bitch is so badly hurt, going by human births we would be stitched by now, antibiotics and morphine are going to be good for so long, perhaps the pain will subside in a few days and with general anesthetic I guess it would not be any good for her milk and the pups, so that is why the soft tissue specialist is not being used immediately.
Back to the toileting as already said it is not abnormal, some bitches can naturally store their toilet for a couple of days if must, they are able to shut down that part of their bodies to stay with their pups, as they are their first priority, in the safety of a home most bitches feel safe enough to leave their pups for a minute to toilet which is why popping her out should work but, I guess with the tear too she may be afraid to toilet aswell, so don't panic about this, only if she has not gone in a couple of days.
Please keep us updated on your bitch and what your vet decides to do for her and how she is coping, it is such a rarety for something like this to happen.