Sounds like your baby is improving now and that he is accepting the diet.
Perhaps the tbs pumpkin is too much so I would keep in the teaspoon range.
It seems ok to me if he is only pooping after meals, that is more normal.
It does take a little time for the GI system to heal, so don't panic just yet, he is doing fine. He is getting better and I would leave it for a couple of days before you get another check up with the vet. But of course you would see the vet sooner if your baby showed worse or new symptoms.
So cheer up and don't worry, he will be ok soon
Just saw about the Panacur for parasites. It might be a good idea to get a fecal sample to see if there are any parasites that need to be removed?