Massive Parent-Child and delegate pattern

I'm facing with a complex design problem. Due to a hard designed graphic I can't use Apple navigation pattern as UINavigationController or other ones. This is the app diagram

Black arrow: protocols direction Blue arrow: parent-child pattern direction

I created this flow because I want to maintain the code inside the single ViewController clear and isolated: I thought about them as modules that they can be used somewhere in other apps. The RootViewController is the MainVCs position manager. It decides which is the current view-controller that it must be showed and it configures it based on its status (modified by delegate methods). The single MainVC doesn't know that RootVC exists and it call Root using protocols. The single ChildViewController doesn't know that its MainVC exists and it call the Main using protocols and so on.

Code is clear and much easy to understand, my purpose, but when I have to apply a modify to the skeleton (RootVC) from the ChildViewControllerN, child of the umpteenth ChildViewController, child of the umpteenth MainViewController, I have to propagate the protocol until the RootViewController.

My first question is: is this pattern correct? What do you think about it?

My second question is: is there a limit point where I haven't to use delegate pattern but something like KVO?