Currently there is no way to modify the popup message in the ways you are asking. I submitted a feature modification request for this very change, but no word if we will actually get this or not.
On that topic though, It would be nice to be able to prevent the button from showing up in the alert message. Some organizations may have no desire (at least in the short run) to entertain overrides. -The process for overrides in prohibitively awkwared anways.