First I want to say that I know what you are going through and I really feel for you.
The symptoms that you describe are exactly what we went through with our Rat Terrier - he had been a part of our Family (Rescued) for 13 years - still very active until one day - the vomiting. It turned out to be Lymphatic Cancer. We chose to operate to remove as much of the offending Lymph Nodes as possible. He was like aPup again, wild and feeling great. Then about 12 months later he woke up one day and vomited again, the Cancer had returned.
Being that your Pup is so young I find it hard to believe that he could have Lymphatic Cancer to the advanced state that would present these symptoms but I would certainly prepare yourself for such a diagnosis. Wait until the Biopsy comes back, but you might want to discuss this with your Wife.
Again, I'm verry sorry to hear of this.