“Does this sound like the end of the tribulation?”
Yes, exactly like it, when you compare it to Revelation 19:11 through Revelation 20:6
“Who repopulates the world after the tribulation if Christ comes to take away all of His people from the Earth and then slays every ungodly person?”
Where does it say Christ “slays every ungodly person” at the end of the tribulation? Or that Christ takes away all of His people, never to return to Earth?
“Revelation 20:8 specifically mentions a world at the END of the Millennium...”
I’m glad you acknowledge that Rev. 20:8 is after the millenium, because that means the directly preceding events, in 19:11 through 20:6 come directly before the millenium, or at the end of the tribulation, and those events include the resurrection spoken of in all the verses that pre-trib rapturists love to quote.
“Where does it say Christ “slays every ungodly person” at the end of the tribulation?”
Matthew 13 and Luke 19 talk about this “end of the age”—this age prior to the Millennial reign. They aren’t going to just go on living since the King will rule with an iron fist at this point.
“Or that Christ takes away all of His people, never to return to Earth?”
They clearly return with Christ in Revelation 19 & 20 to reign with Him.