Hello,
All the widgets that you see in the demo of the theme Splash will be accessible to you.
Yes, you can change the background as you like and if you are unable to change it through the theme options you can make a forum post and we will give you custom CSS on how to change it.
Yes you can remove that copyright.
The size of the content picture slider can be altered but this would be something custom. It depends to what size you want it to be, we may be able to help you with that.
I'm not sure what you mean by this: Can this widget link to recents posts and cycle through their headline post photos?
Increasing the width of the template can be done with custom CSS but please advised that it may lead to other elements on the page being misplaced and will force you to inquire for additional changes. We may not be able to support you with additional custom changes depending if they are extensive.