I'm so sorry to hear about Drexler, there is an article in the YT library, I thought I'd link here :
Information on Help for Vet Bills maybe this will be usefull for you.
If you've only been working with regular vets; then I think it is time to go to the specialists.
The liver group posted with have tons on information for you, including good vet hospitals.
Keep us posted
and good luck with your boy. Also for sure contact the breeder, they need to know about is ongoing condition.
One other thing look up the Puppy Lemon laws in your state.