The way to tell if your baby has pneumonia is to listen for clicking when he breaths. Sometimes it is very subtle. I would put him next to my ear and listen for clicking. If you hear clicking, it is imperative that the baby receives antibiotics.
Ciprofloxacin or Baytril would be the best but others can be used also. Just let us know what you have and we can help you. They respond very fast to antibiotics. If you don't have any antibiotics, maybe a family member or friend has an antibiotic.
If you are able to get the Esbilac puppy formula, it would be great. The KMR kitten formula will cause problems for the babies and is not recommended. Baby squirrels are fed 5-7% of their body weight per feeding. You would need a scale to weigh the babies in grams. Example: if the baby weighs 50g the proper amount per feeding would be 2.5-3.5ml. The proper feeding device is a 1ml (cc) syringe.
I hope this helps. Our offer of help still stands.