Sorry to here about your young dog being sick, It sounds like you have done everything right here. I'm sure the blood tests will tell you what is going on. You are a good owner and I pray everything will be fine for your good friend.
I really hope your dog will be ok.
Did they test him for Lyme disease?
Lyme disease (from an infected Tick bite) can easily infect a dog who is outside a lot, in the undergrowth or fields, woods, etc.