For me, appeals to free will and human agency have never been particularly satisfying when considering the problem of evil.
If anything, I think they might tell us more about how we conceptualize God than how we conceptualize evil.
I will need to spend more time studying the philosophy of religion before I can more fully respond to this question, but I found this video from the Center for Philosophy of Religion at the University of Notre Dame to be both helpful and enlightening about this questions.
Marilyn McCord Adams is a philosopher at the University of North Carolina. She is also an ordained Episcopal priest.
What do you think of her comments in the video? What do you think of this question?