Honestly, I have no idea. I haven't had any issues accessing content online, but I have read that it doesn't handle video all that well. In such, you will want to double check some other sources. Not sure about itunes either. IF either of them require installed software that you can't get as a Google Chrome addon/plugin, then the answer may very well be no.
You can't install software on the Chromebook like you would a laptop/desktop. It all works in the cloud or via browser plugin's.
Shouldn't be a problem using any cloud storage, including amazon. Just don't expect to use any SD cards, usb storage or external hard drives without a fight. You can only use online apps in the chrome store, so no iTunes.