Sufficient proof can only be validated if Pakistani Investigators or diplomats are allowed an access to Ajmal (or wheatever his name is). India should have no problem in giving the access as by its own claim Ahmal is a Pakistani Citizen. If its proved beyond doubt, Pakistani should (and will) take strong actions against such elements.
As far as tour cancellation is concerned, it was on the cards anyway looking at BCCI's past behavior and coming elections.
How about acting against Masood Azhar (who has conveniently disappeared), Hafiz Saeed & Dawood Ibrahim ?? Pakistan obviously has access to them.