It is not word games. God is the author of the Book. Evil exists. Trees exist, we exist, all of us are authored by God.
That does not make God an evil tree with a man's trunk.
God has complete control over evil. In fact, several hostile websites have claimed that Calvin assigned evil to the devil and man alone, disavowing it from God. So from the hostiles, I am getting two different stories, both of them unlikely.
If you cite any relevant texts from Calvin to support the view that Calvin attributed evil to God as "moral character" please do so.
Also, classically, God does not have "moral character." God has attributes and essence undivided. As Calvin, Aquinas and Augustine all held to the doctrine of Divine Simplicity, it is unlikely Calvin would amend the doctrine of Divine Simplicity as you state to add evil as either essence or attribute.