Friend, I am sorry you are going through this with your puppy. In response to your question, yes, you are right; parvo is one of the medical conditions that needs to be ruled out based on the symptoms that you are describing. There are many other medical conditions like ingestion of a foreign body, other types of infections, intestinal parasites, etc. to name a few causes that also need to be ruled out. To determine the exact underlying cause he will need a hands-on examination by your family veterinarian, fecal analysis, blood work and possibly x-rays. Unfortunately, we are somewhat limited as to what you can do at home, I am sorry. But, in any case of vomiting or diarrhea, the first thing to do is give the gastrointestinal tract time to rest. You see, if you start pushing water or food orally he will continue to vomit making things worst. So, once you rest the gastrointestinal tract then you gradually introduce water then food. This is what you can do until he is seen by your family veterinarian in the morning:
1- Do not give things like Pepto Bismol or Imodium.
2- No food or water for 3-4 hours. Need to give his gastrointestinal tract time to rest.
3- After 3-4 hours offer a small amount of water. Wait half hour, if no vomiting, continue to give small amount of water every hour or so. Keep him off food for 8-12 hours. Then, you can offer a small amount of rice (50%) and boiled boneless chicken or ground beef (50%) 4-6 times a day.
4- Follow up with your family veterinarian for a hands on examination and supportive care (IV fluids, antiemetics, etc.).
My goal is to provide you with excellent service - I hope I've provided the information you were seeking, if you feel you have received anything less, please reply back as I am happy to address follow-up questions. Kindly rate me when you are done.