Yes, it's a very good idea. Please accept that you'll never get them to look exactly the same as each other, but we should try.
Make sure you have your Displays set to "Extend", never "Duplicate".
No, it can run as many as you wish. Well, if there's a limit I've never found it. I've got mine running four profiles at the moment.
No, absolutely not. Prints are prints. Your lab doesn't change the way they print just because one of their customers got a new computer, you know?