Isn't there a contradiction between the fatwa permitting masturbation with the wife's hand even if madhy or mani is discharged, and the fatwa prohibiting the wife from caressing the penis if it has impurities or madhy on it?

There is no contradiction in the fatwas, for the touching of impurity when a husband masturbates with his wife's hand is not necessary, and if any such thing occurs, it is forgiven; because touching impurity is forbidden only when there is no need.