1. At this point you can’t edit menus for ‘Administrator’ role. This is done on purpose, if a user screws up their configuration, they will will have at least one role to restore everything back. I’ll add a to do list item to find a better alternative.
2. Override Type Soft allows you to access the page using its URL when its hidden. Hard doesn’t allow you to do that. Do you have those menus hidden for that role?
3. Not at this moment. That functionality uses the standard WordPress message when you don’t have access to a back end page.