He was given power to take everything including his sons and daughters from Job. For this purpose the Son of God was manifested, that he might destroy the works of the devil. Dear Brother, I don't think Satan is a theory. He is on many pages of the New Testament. I am Historicist and agree with you on this because it referred to fall of the Roman Empire.
Revelation is History in symbolic language right up to the present time.
My fallen angel theory is not from Revelation. And lest I should be exalted above measure through the abundance of the revelations, there was given to me a thorn in the flesh, the messenger of Satan to buffet me, lest I should be exalted above measure. I regard the Greek New Testament from the received text as inspired. Surprisingly, when Erasmus translated Revelation, he had to use the Latin Vulgate because he had no original translation. I am always open to new revelation and change, and if you can answer this, still convincing me there is no Satan, I will most certainly reconsider my position.