What was the purpose of the Se'udah that they made with Yisro?
When did they make the meal?
Ramban #1: As soon as he arrived, before they even arrived at Sinai. 1
Ramban #2: Only much later, after he had settled down, and after he converted with Milah, Tevilah and bringing a Korban. 2
Moshav Zekenim: It was not before Matan Torah, for Moshe was constantly going up and down Har Sinai. Rather, it was on Yom Kipur! 3
Da'as Zekenim (13), Hadar Zekenim (13): It was two or three days from when he descended from Har Sinai (on Yom Kipur). The Torah is out of order.
Where was Moshe - who went out to meet him and caused him all this Kavod?
Rashi and Targum Yonasan: Moshe was serving the guests.
Rashbam: Seeing as Moshe was the host, it is obvious that he was there, and it is not therefore necessary to mention him by name.
What are the connotations of "Lifnei ha'Elokim"?
Rashi: It teaches us that someone who partakes of a Se'udah at which Talmidei-Chachamim are sitting, it is as if he had benefited from the glory of the Shechinah.
From where did Yisro get animals for Korbanos? It does not say that he brought animals!
Moshav Zekenim: He bought them.
From where was the bread for the meal?
Moshav Zekenim: It was normal bread. Manna was only for Yisrael, who were afflicted. Yisro brought bread; he was rich, and would not leave without bread. The others ate with him to honor him. Also, they desired to eat bread. 1
Why would Kedoshim like Moshe and Aharon desire to eat bread? This is fine if we will say that there was no Torah Mitzvah of Birkas ha'Mazon on Manma (see Daf Al ha'Daf Brachos 48b citing ha'Gaon Rav Y.S. Elyashiv Ztz"l - PF)