1)
Why did he say to cast him to the sea?
1.
Malbim: I do not want to repent or go to Ninveh. The storm is not to return me to my land or Ninveh, rather, to punish me for rebelling against Hashem's word. It is not to punish you for taking me to Tarshish. When I will drown in the sea, it will quiet from you.
2)
What is the meaning of "v'Sheli"?
1.
Radak: It is due to me, i.e. my sin.
