These are things that David says he will do, along with "seeing the prosperity of your chosen." The words "I will" may be repeated here. Alternate translation: "I will rejoice in the gladness ... and I will glory" (See: [[rc://en/ta/man/translate/figs-ellipsis]])
Here the phrase "your inheritance" refers to the Isrealites, who are Yahweh's chosen people. Here "glory" means "to boast about" something; in this case they are boasting about Yahweh. Alternate translation: "boast of your greatness with your people" or "boast with your people about you" (See: [[rc://en/ta/man/translate/figs-metonymy]])