[souffle]

Can you take him back Carly? When they get to a situation where they cannot control their body temp the body system is shutting down and he is unlikely to make it.
The only way would be intensive nursing with fluids and warming in an incubator and even that may be too late I'm afraid.
Did he have diarrhoea to get the wet tail diagnosis? If he has had it then sometimes the bowel has been so badly damaged that they cannot absorb food and will fail to thrive.
If you cannot see a vet today either to ease his path or have intensive nursing then keep him very quiet and calm and offer fluid on a spoon. Talk gently and let him know you are there for him and he can take the path he chooses. Tell him he is loved and safe journey.
I hope his path is gentle.