What is the Pasuk referring to when it says "v'Asah la'Par ka'asher Asah le'Par ha'Chatas?
Rashi #1: It is referring to the obligation to burn the Yoseres ha'Kaved and the two kidneys.
Why did the Pasuk not write the Din of the Yoseres ha'Kaved and the two kidneys here specifically?
Rashi (on Pasuk 19 - citing Tana de'Bei R. Yishmael): It can be compared to a king, who is angry with his close friend, and who minimizes his sin out of his love for him.
Why does the Torah mention that Moshe took the staff after writing that he returned to Egypt?
Rashi: To be sure, he took the stick before leaving for Egypt, only the Torah does not always follow the chronological order.
Seforno: The beginning of the Pasuk is referring to Moshe's returning to Yisro from the desert; 1 And the Pasuk then tells us that, after depositing his wife and children with his father-in-law, he returned alone to Egypt, having taken his staff with him. 2
If Moshe took his wife and sons with him to Egypt, as the Pasuk implies, how is it that, at the beginning of Yisro, Yisro brought them to Moshe from Midyan?
Rashi (in Yisro): When Aharon met Moshe at Har Sinai he questioned the wisdom of taking his wife and children to Egypt, so Moshe sent them back. 1
Ramban #2 (citing the Ibn Ezra): Initially, Moshe did indeed take Tziporah and his sons with him. However, when the incident recorded shortly after (Shemos 4:24-26) occurred, it was not possible for them to continue to travel, so, not wanting to delay fulfilling Hashem's command, he left them in the inn with instructions, that, when Eliezer will have recovered, they should return to Midyan. 2
Seforno: Refer to 4:20:3:2.
In fact, Yisro advised Moshe to leave them in Midyan, but Moshe insisted on taking them with him - so that they should not miss Ma'amad Har Sinai. Yisro conceded to Moshe, and Hashem corroborating Moshe's decision, ordered him to return to Egypt with his wife and children (Ramban citing the Midrash).
Why does the Torah not mention the birth of Moshe's sons, and the reasons for their names here (only in Yisro, Shemos 18:3 & 4)?
Ramban #1: In fact, in spite of the term "Banav", only Gershom was born, and Tziporah became pregnant with Eliezer on the way to Egypt or in Egypt, assuming that she actually went there. 1
Ramban #2: Although Tziporah was pregnant with Eliezer, he was born only after Hashem spoke to him by the Burning Bush. And because Hashem's command was incumbent upon him, he did not circumcise him before departing for Egypt; nor did he manage to name him after circumcising him due to the incident with the angel. And it was only after he arrived in Egypt and discovered that he was no longer threatened by those who sought his Soul that he named him Eliezer - "Because the G-d of my father assisted me ... ."