In the Shadow Diamond part, you need 53 Thieving to picklock the chest. However, you should also add that even if you drank Bandit's Brew just to reach 53, you will not be able to picklock. You need a solid 53 Thieving to attempt to picklock the chest.
You should also add that Ancient Magicks cannot be auto-casted by modern staffs. Only Ancient Staff is able to do that.