You can also try, this: when you are on your fb profile page, remove the https://www. in front of facebook.com and type graph instead and press enter. then youll find your facebook id. easy piece of cake :)
You can only choose one companion at a time. The level will always automatically choose the best option, of the companions you have already gathered, regarding on the level. But you are free to choose any of the other two that are next best. It may depend on if you want to use less beans or concentrate on other cropsies if…