This can be stated in active form. AT: "I think of the world as already dead" or "I treat the world like a criminal God has killed on a cross" (See: [[rc://en/ta/man/translate/figs-activepassive]])
The words "have been crucified" are understood from the phrase before this. AT: "and I have been crucified to the world" (See: [[rc://en/ta/man/translate/figs-ellipsis]])
Possible meanings are 1) the people of the world, those who care nothing for God or 2) the things that those who care nothing for God think are important.
Possible meanings are 1) that believers in general are the Israel of God or 2) "may peace and mercy be upon Gentile believers and upon the Israel of God" or 3) "may peace be upon those who follow the rule, and may mercy be upon even the Israel of God."