1)
What was Hashem referring to when He said, "Lema'an Har'osecha Es Kochi"?
1.
Rashi (to Yeshayah 64:1): He was referring to Keri'as Yam-Suf, where Egypt witnessed Hashem's strength in full force.
2)
Why was it important for Pharaoh to see Hashem's strength?
1.
Seforno: So that he should do Teshuvah. 1
1
Seforno: Because Hashem does not want the Rasha to die - Yechezkel 18:32. According to the opinion that Pharaoh survived Keri'as Yam-Suf and became king of Nineveh, he did indeed do Teshuvah.
3)
What did Hashem mean when He added, "u'Lema'an Saper Shemi..."?