What is the force of the word “all”?

The term itself is comprehensive, encompassing every member of a given group. So the question is whether the group implied here is the totality of humanity (and hence all refers to every person on Earth). That clearly is not the case (see John 17:9). Instead, we need to recall that Jesus instructed John to send this book to the seven churches that are in Asia (Revelation 1:4, Revelation 1:11). These churches (with their members, on the caveat caught in the word share in Revelation 22:19) may be assured that God’s grace in Jesus Christ is theirs.