1)
What is the meaning of "Ki Va Yerushalayim Likras ha'Melech"?
1.
Radak: When David came to Yerushalayim, Mefivoshes came to greet him. It is as if "Va" is written twice.
2.
Malbim: This shows that David erred also in his inference about Mefivoshes' mindset that he did not fear to remain in Yerushalayim [because he supported Avshalom]. He was hiding outside Yerushalayim, and returned only now!
2)
What is the meaning of "Lamah Lo Halachta Imi"?
1.
Rashi: Why did you not leave Yerushalayim when I left?