Yes, all of the fish in the tank could get it. Even if only 1 fish in your tank has it, treat every fish to make sure the parasite gets off. I noticed one day that one of my little fishie friends had...
At this time, no. No one has ever gotten Ich from an aquarium, so if it hasn't happened yet then I think you're safe. Even if you are exposed to it, it won't do anything to you.