Your little guy most likely had a "cleft palate", which caused the aspirated milk. This is common with some Dwarfs. I have a friend who had a little dwarf filly who had the same problem. They noticed that she always had a bit of milk coming out her nose when she nursed, but they had no idea she had a cleft palate until she got sick with pneumonia at a few months old. The vet said they could fix the cleft palate...but they had to wait until she recovered from her pneumonia first....which she never did.
Anyone who has a dwarf born, should check to be sure there is no cleft palate. If there is....you need to make a choice. Surgery to correct it....or put them down humanely, because they will, eventually get pneumonia from aspiration of milk.