1)
Why did Hashem say that He will not hear their fast? The verse did not yet mention Tefilah!
1.
Radak: There is no fast without Tefilah and screaming.
2)
What is the meaning of "Rotzam"?
1.
Radak: I will not accept them. Their Olos and Menachos will not please Me.
3)
Why does it say "Ani Mechaleh Osam"?
1.
Malbim: I will do so Myself, and not through Hester Panim.