Here the word "he" refers to Jesus. Except where otherwise noted, the word "you" in the book of Acts is plural. (See: [[rc://en/ta/man/translate/figs-you]])
This is a reference to the Holy Spirit. Alternate translation: "the Holy Spirit, whom the Father promised to send" (See: [[rc://en/ta/man/translate/figs-metonymy]])
If you translated the previous phrase to include the words "Holy Spirit," you can change the word "which" to "whom." Alternate translation: "about whom Jesus said"