Here "the circumcision" is a metonym that refers to the Jews. You can translate this in an active form. Alternate translation: "Jesus Christ has become a servant of the Jews" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-activepassive]])
These are the two purposes for which Christ became a servant of the circumcision. Alternate translation: "in order to confirm the promises ... and in order that the Gentiles might glorify God for his mercy"
Here "the fathers" refers to the ancestors of the Jewish people. You can translate this in active form. Alternate translation: "the promises that God gave to the ancestors of the Jews" (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/figs-activepassive]])