1)
Why was he concerned for "Shelom Esther u'Mah Ye'aseh Bah"?
1.
Torah Temimah citing Esther Rabah: He was concerned for one soul. Hashem said, in the end you will seek Shalom of an entire nation - "Doresh Tov l'Amo v'Dover Shalom l'Chol Zar'o" (10:3)!
2.
Vilna Gaon: (a) Mordechai knew that she is a great Tzadekes. The good that a Rasha does [for her] is bad for her; it pains her greatly. He feared lest she get ill from pain. (b) He feared lest they kill her because she did not want to go.
3.
Malbim: He wanted to know if they will punish her or expel her for not going willingly. He was sure that she will be punished for this rebellion.
