Here "sat" represents ruling or leading. Chiefs sat down when they made important decisions. Alternate translation: "led them as their chief" (See: [[rc://en/ta/man/jit/figs-metonymy]])
This phrase means that Job actually was one who comforted people. Alternate translation: "I comforted them when they mourned" (See: [[rc://en/ta/man/jit/figs-explicit]])