so sorry your baby is ill, I really don't have any idea of what you could do, except to either get a second opinion (yes, I know that's more money) or try to raise some money (friends, family, maybe the breeder you got your dog from?). Some Vets will allow payment plans or they usually have applications for credit (relating to pets).
Is your tzu at a hospital that has specialists? Not sure where in Canada you are but there are also some Vet Colleges that might be able to help out.
I know how you are feeling, I lost my Harley in August to an unexplainable illness (seizures and blindness) and did spend the thousands to see if we could do anything. In the end, I couldn't watch him suffer anymore and sent him to the Bridge.
Good luck.....