I'mma start loading you up with n00b questions since youv'e been such a good sport and it's faster then researching it myself. Can you keep more then one in the same tank?
umm I think you can...they aren't terribly active.
You just need to make sure you have a tight fitting lid cause they are jumpers! mine hasn't tried to get out yet and I have had him for about a year.
I wouldn't even bother with the salt unless it appears to get infected. You can if you want. It won't hurt. This will occur often and you will be amazed at how fast these little guys heal....