I have read many of your posts and respect your intellect, but you of course realize that Satan is a "Spirit being". His torment will go on forever. On the other hand, humans thrown into the Lake of Fire will have a different kind of torment. That would be eternal separation from God. This is also called the second death [Rev. 20:14]. The dead are aware of nothing [Ecclesiastes 9:5].
Let me ask you a question. A man and a woman have children who turn out to be incorrigible sinners and unrepentant. The man and his wife, both God fearing and just, have failed in their efforts to convince their offspring of the error of their ways and you believe that a merciful God would allow these parents to eternally witness their children burning in a "Hellfire"? I think a merciful God, knowing that these children would be forever unrepentant, would destroy them in the Lake of Fire along with the Beast and False Prophet. I don't think a merciful God would allow these parents eternal anguish.