What was the gist of her complaint against her husband (See also Pasuk 17)?
Ramban: The Egyptians hated the Ivrim, to the point that eating at the same table was considered an abomination. They would acquire them to work in the vineyards and as gardeners, but not to work in the house. Consequently, her husband 1 had wronged them all by bringing Yosef into the house and appointing him as manager, for him to jest with them. 2
What did Potifar's wife ask the members of her household to 'see'?
Targum Yonasan: She placed the white of an egg of her bed and pointed to it, making out as if it was semen. 1
Ohr ha'Chayim #1: Here she was trying to incite her household against him, through envy - see, [my husband] raised a stranger over us!
Ohr ha'Chayim #2: See, so you can testify about this.
What does "Letzachek Banu" mean?
Rashi (21:9): 'Metzachek' is an expression of sexual immorality.
Ramban, Targum Onkelos and Targum Yonasan: It means literally 'to laugh at (to make fun of) us'.
Seforno: Potifar's wife was accusing Yosef of acting in a lewd fashion, which clearly indicated his intention of being intimate with her.
Why here, did Eishes Potifar say "Letzachek Banu", whilst in Pasuk 17, when relating the incident to her husband, she said "Letzachek Bi"?
Oznayim la'Torah: Because here she was trying to incite all the people against him, 1 whereas when speaking to her husband she was stressing that Yosef accosted her - the most beautiful of women, in order to arouse his ire against him.
Malbim: She aroused them - if he did so to me, all the more so he will do so to you!
Ha'Emek Davar: She understood from Yosef's claims that he cannot fulfill his desire with his master's wife for reasons (Hakaras ha'Tov, fear of demotion) that do not apply to the others, and that he truly enticed them to Zenus. 2
What is the significance of the loud voice? Why did she need to mention it?
Rashbam: As mentioned earlier, there was nobody in the house, since they were all celebrating. Consequently, had she not cried out loud (according to her version of the story), Yosef would have raped her.
Ha'Emek Davar: It is proper for one who is shocked at such enticement to scream in a loud voice.