Is it possible that the snake cant shed if his stomach is too fat or will it cause the skin to tear or something?
This has happened to me where I've completely missed the signs (easier in the lighter coloured Corns). The snake ate, and actually started to shed in the feeding tank. The shed reached the mouse bulge and just stopped. As I'd caught it as it was happening, the shed was still damp. All I did was tear the old shed that was already loose, so that it could split over the mouse bulge. I popped the snake back in her usual tank and she continued to shed perfectly without a care in the world. No regurge.
So that scenario can happen, but in this case, was no problem at all.
With a bad shed that leaves small patches of the old skin behind, it's usually not a drama as long as you catch it and deal with it promptly. The most likely bit to be left behind is the tip of the tail. If you do miss it, then the tail tip can be constricted by the old sheds (which build up if the owner is being really unobservant), the blood supply will be cut off and it will die. Usually the loss of a small bit of tail tip isn't anything more than a cosmetic issue - it's probably one of the hazards of life in the wild. Putting some antiseptic on it and keeping it clean until it heals will ward off further problems.
However, a lost tail tip does have the potential to leave an open wound behind which can get infected, cause septicaemia and ultimately death. So although the chances are very remote indeed, I've certainly heard of this kind of shed problem causing a snake's death on more than one occasion. In those instances however, the affected part of the tail was quite large and the owners really hadn't been paying attention up until the crisis point.
I can assure you that this is absolutely never going to happen to your Corn, which looks to have landed with a very conscientious and caring owner!