I'm sorry for your loss =( Sounded like he had fungus and with the shock of the move, was too much for him.
For future: Never use bottled water, there are beneficial bacteria and nutrients in tap water. Use tap water (even if it hasn't been sitting over night) with the proper chemicals to rid of chlorine over bottled water. Water should be 76 at the very lowest. 78-80 is prime. They can survive in the lower temps for a while, but they will always end up lethargic and sick at some point if in it for extended time. You don't want anything less then 1 gal. With 1 gal you will be doing 1 50% and 1 100% water change per week. Keeping him in a smaller container is okay for a short time, but you will need to up the water changes to 100% every other day until you get a bigger home. Also, tapping on the tank/glass will add stress. Instead just run your finger along it or talk, it's less startling.
Again, I'm sorry you lost him, he looked like he was a sweetie.