1)
Why did he call Amnon "Aminon"?
1.
Radak: This was for disgrace.
2)
Why is there the prefix Vov before "Shomemah"?
1.
Radak: The prefix Vov is superfluous, like "va'Yisa Avraham Es Einav" (Bereishis 22:4).
2.
Radak citing his father: In such cases, a similar word was omitted, e.g. she was sad and depressed.
3)
Why should she be quiet?
1.
Malbim: It is for the three reasons why she did not consent. (a) Your honor - you are not disgraced for being secluded with him. He is not a stranger. He is your brother! (b) Due to his honor, be quiet (lest he be disgraced more). (c) Due to the action itself - what was, was. Forget it!