I agree also that Hamlet is not crazy. He is disturbed. He is disturbed because he has to choose between his mother and his father. This is the crux of his dilemma.
If he honors his father by revenging his father's death, he will be killing his mother's husband and destroying her happiness. If he chooses to honor his mother's happiness, he will be letting his father's death go unpunished.
There is a great weight in his decision.
I don't think we can look at the ghost scenes as being evidence of Hamlet's madness. We have to look at them instead as narratively essential moments, without which Hamlet's decision would be much less clear and therefore less dramatic.