Oh, dear. That poor, poor puppy. The itching is terrible.
My Petie (Golden Retriever) got mange/scabies. I have never heard of using a spray. He was treated with Ivermectin given by injection. It took three injections to clear it up.
This is an excellent article from Marvistavet:
Sarcoptic Mange
I got the itchies, too. While humans aren't hosts, the mites will bite people and the itching is terrible, isn't it? I washed all my bedding everyday until we got rid of it.
Can you find a vet that you can communicate with better? This poor little guy has to be just miserable and since he is so tiny, you have to be very careful how you treat it.