1)
Why did he say "Hashem Elokei Yisrael"?
1.
Rashi: This is an expression of a Shevu'ah.
2)
What is "Machar ha'Shelishis"?
1.
Rashi: It is the third today from today. Perhaps he will not be astonished [at my absence] tomorrow, but he will be astonished on the third day.
2.
Malbim: First I will wait to see if he questions your absence. If not, on the third day I will speak to him.
3)
What is the meaning of "v'Az Lo Eshlach"?