The words "to his face" are a metonym for "where he could see and hear me." AT: "I confronted him in person" or "I challenged his actions in person" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The reason Cephas was afraid can be stated explicitly. AT: "He was afraid that these men who required circumcision would judge that he was doing something wrong" or "He was afraid that these men who required circumcision would blame him for doing something wrong" (See: [[rc://en/ta/man/translate/figs-explicit]])