You have to go into the "People" app to edit contacts. If you want to remove one from your favorites list, you need to edit the contact, go to Group and uncheck "favorites".
Also, to set the widget action for a contact, click menu, more, set widget action and select new message. One limitation here...you can only set one widget action per contact, so you can't set the same contact to dial mobile and to also send a text message. As a work around, you could set the widget to view contact and then select what you want to do from the list. It's more steps, but it's the only way to do multiple things for one contact via the favorites widget.