1)
What is "Shalom l'Avdecha"?
1.
Rashi: If he is not upset, he does not intend to kill me.
2)
Why would being upset show that he wants to kill me?
1.
Rashi: He is upset that I am not available for him to kill me.
3)
David omitted two possibilities - perhaps Sha'ul will not ask at all, or he will ask, and not comment when he hears!
1.
Malbim: He discussed only the two cases in which his intent will be known. In the other two cases, it will remain a Safek.