A Question Only my Christian Friends can Answer

Okay, so if the Devil is evil and the enemy of God, why does he punish bad people in Hell?

If The Devil was really against God, wouldn't he be nice to the people He has condemned to Hell, instead of doing God's dirty work for him?

And please don't tell me to look this shit up in the Bible, because there is no Devil in the bible. There is an angel ...called Satan in the Book of Job, but he is completely subservient to God

The snake in the Garden of Eden was just a talking snake

Christians said it was the devil centuries after Genesis was written

There is a fallen angel mentioned in the New Testament (though he is never called Lucifer) but he's stuck in Hell being tortured for all eternity. He doesn't run the show himself

So what I'm asking is why do Christians, without even following what's written in their own holy book, believe there's a Fallen Angel that really fucking hates God, but still helps him out by taking care of all the evil people?

Not trolling here, I'm honestly just curious about this discrepancy between what Christians believe the Devil to be, and how he actually acts