Question everything including this theology. John MacArthur says when in doubt interpret literally. I do not believe they are from the past but sealed for a purpose in the tribulation. You are in more danger by attempting to see symbols I think.
Believing what is says Chapter 1 vs. 1 is a good start at believing literally: “The Revelation of Jesus Christ, which God gave him to show to his servants what must soon take place, and made it known by sending his angel to his servant John.” Not really hard to understand at all.
How do you interpret apocalyptic symbols literally?