The “Lake of Fire” is symbolic for the gold refiner’s crucible, because God will refine unbelievers. The author uses Proverbs 17:3 to back this claim. The reason the Apostle John mentions “sulfur”/“brimstone” in Revelation 20:10 is because sulfur was used to refine gold. Otherwise, why would he mention sulfur? This is symbolic for God refining/purifying sinners.
The Greek word translated as “tormented” is “basanizo” which originally meant “to test the purity of gold”. Again, this is symbolic for God refining/testing sinners until they are pure.
Then the obvious argument about “forever and ever” really meaning “in the ages of ages” in the original Greek. It’s a very interesting video, and I’d highly recommend it.
EDIT: I should also mention that the “Second Death” referred to in Revelation is a SPIRITUAL death, according to this author.