Hezekiah uses a question to emphasize he has nothing left to say. This can be written as a statement. Alternate translation: "I have nothing left to say." (See: [[rc://en/ta/man/translate/figs-rquestion]])
This refers to the rest of his life. The meaning of this can be made clear. Alternate translation: "the rest of my life" (See: [[rc://en/ta/man/translate/figs-explicit]])