I am just catching up on how Buster is doing from yesterday... My goodness this much be so stressful on the whole family . I hope that Buster is feeling better this afternoon and his blood sugar has stabilized.
i am thinking that 2lbs is big enough for the vet to get a blood sample.. They really need to do further tests on Buster to rule out any other possible health issues. Just to be on the safe side.
Continue to force Buster to eat , and try not to change his foods around too much, because this will further upset his tummy. Canned pumpkin will settle his belly down, which has already been suggested. Buster is very lucky to have such dedicated human parents and a loving family

You are correct that bring home a little puppy is so much work! Especially when the pup is not feeling well. It is very good that your able to stay at home with him today and care for Buster. he needs all the love and attention from you as well as getting him to eat often, and to be watched over. I hope Buster is going to be ok and feeling better soon .