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.
I can appreciate your feelings about this however Rev. 21:4 says that sort of sentimentality will be no more. Believing parents, just like the believing martyrs, will understand the just and righteous judgments of God and worship Him for it. Satan is a spirit being and the antichrist and false prophet are humans. That does not take away from the clear and explicit statement that they, not just Satan, will endure torment for ever and ever. Rev. 20:15 says that all those not found in the book of life will suffer the same fate; those are humans also.
It's not a very good idea to try to reason your way to correct theology based on an emotional appeal.
The blessed in heaven see things as God sees them. They will have the same sorrow at seeing damned souls in hell that God has. However, that sorrow is tempered by the certain knowledge that those souls freely chose their fate, and God simply respected their choice.