It's so hard, our dog Tomas was like that deaf, blind, wobbly, bit confused right up until he eventually died on his own terms curled up on the sofa, really sweetly and peacefully, but for a good couple of months we were considering what was in his best interests. Our vet said he's not in any pain, he still responds positively to you when you touch him and you interact with him and he's still enjoying treats and what not so there is no medical need for him to be put down and he thought he might just be entering his stage to die, which he was. since your dog isn't eating at all however, that might be different but if he's drinking and still waggy I'd be inclined to take your vets ad=vice, as dying is a process not a one second event with animals particularly I think. It's so horrible and I hope you are okay x