Hurray! I can say w/certainty that both Spirit (who started w/urinary tract inf.) and Bob (who had a good case of pneumonia w/cyanosis) are nicely recovered! Spirit finished her meds a few days ago, and Bob just has a few days left of his diuretic to take (not in his opinion!!) and we're done. This episode made me realise that it's true that every day really is a gift and can all change overnight.
Guard your cat's health and knowledge is really power when it comes to their illness: had I known that coughing when not associated w/hairball is NOT normal I'd have brought Bob to the vet much sooner. If you have doubts or questions about your cat's behavior or well-being don't worry about bothering your vet, that's their job.
Here's to long, happy, healthy lives in our cat's "forever homes", and thanks again for all the support your guys gave me!!!