1)
Why was he mute?
1.
Radak: I cannot scream 'injustice'. The pains did not come to me from people, rather, from You. Also against You I cannot scream, for it is due to my sins.
2.
Malbim: Now I am silent from the above question (the nature of the Nefesh), for it was clarified for me that man's formation is unlike that of other acts of creation that are attributed to the land - "Totzei ha'Aretz Nefesh Chayah" (Bereishis 1:24). His formation is attributed solely to You - "u'Neshamos Ani Asisi" (Yeshayah 57:16).
2)
What did Hashem do?
1.
Rashi: He brought the affliction on us.
