Revelation 1:1 is relevant to Revelation, not to the entire Bible. Revelation is not a parable, but a vision. Even so, though most of Revelation is symbolic, some parts are not.
Revelation is a vision as prophecy given through a parable. Apply that to Chapter 20 now that you do agree it at least applies to one book. What does the metaphor "thousand years" represent?
It is used as a metaphor 9 times throughout the Bible to represent a unmown .(we walk by faith) . What do you think the phrase thousand years represents in that parable?
Which parts are not?