1)
Sha'ul announced that he is gathering to make war against David in Ke'ilah. What is the Chidush that David knew?
1.
Malbim (8, 9): Sha'ul did not announce against whom is the war. People assumed that it is against Pelishtim, for Ke'ilah was in Pelishtim's hands. David understood his intent.
2)
What is the meaning of "Macharish ha'Ra'ah"?
1.
Rashi citing Targum Yonasan: He is hiding in ambush to do evil.
2.
Radak: He is thinking (plotting) to do evil. This is like "Al Techerosh Al Re'acha Ra'ah" (Mishlei 3:29).