1)
What is the meaning of "va'Yichar l'David"?
1.
Malbim: He realized that he was not properly careful about honor of the Aron; he was upset with himself. Charah Af is being upset at someone else; Charah Lo is being upset at oneself, e.g. "va'Yichar l'Kayin [Me'od] va'Yiplu Panav" (Bereishis 4:5).
2.
Malbim citing Sotah 35a: His face turned [white] like a Chararah (cake).