How horrible for your little pup.
If a Yorkie vomited 21 times, the vet should've sent him to a specialty or teaching hospital for intensive care.
That is the rectal temperature, right?
He needs to go to a vet that is going to try and figure out what is wrong.
Trying to warm him up at home when it hasn't worked for 5 days seems like a waste of time. I'd get him to a different vet immediately.
If rabies vaccines are required where you live, I would definately find a vet to sign a waiver for Puf.