that switch bodies tool seems OP, did his curse get transferred with him? or did it stay in his body with alice's mind?
If it stayed on his body then that might be the solution to break the curse
It wouldn't help as I think duke wouldn't want to inflict the curse on someone else and he also wants to return to his family so losing his body would be a no no.
Although that is a thought if a person is cursed what carries the curse: the body or soul