What are the two times "Lamah" referring to?
Seforno: Both with reference to the episode of the Burning Bush, Moshe is questioning a. Why Hashem sent him to take Yisrael out of Egypt against his will and b. Why He ignored his request "Sh'lach Na be'Yad Tishlach"!" 1
Why is the word "Matzasi" missing an 'Alef'?
Ibn Ezra: It is common for a word to omit a 'Yud', a 'Hey', a 'Vav' or an 'Alef'. 1
See also Ba'al ha'Turim.
What did Moshe mean when he added "Lasum es Masa Kol ha'Am ha'Zek Alai"?
Seforno: Moshe meant that Hashem clearly intended to place the burden entirely on his (Moshe's) shoulders - as if He (Hashem) had no other leader besides him, and that He should have at least partnered him with someone to the people's benefit.
