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/translate/figs-metonymy]])
Job speaks of how he led the people and how they obeyed him as if he were a king and they were his army. (See: [[rc://en/ta/man/translate/figs-simile]])
This phrase means that Job actually was one who comforted people. Alternate translation: "I comforted them when they mourned" (See: [[rc://en/ta/man/translate/figs-explicit]])