Possible meanings are 1) this is a list with three items, and Paul is addressing three groups of people together, or 2) the phrases "children of the offspring of Abraham" and "those among you who fear God" refer to the two groups of people whom Paul addresses as "brothers."
This can be stated in active form. Alternate translation: "God has sent the message about this salvation" (See: [[rc://en/ta/man/jit/figs-activepassive]])
The word "salvation" can be translated with the verb "save." Alternate translation: "that God will save people" (See: [[rc://en/ta/man/jit/figs-abstractnouns]])