I agree that the Ezekiel 38/39 war has to happen before the Tribulation because it is very likely that is will be this war that produces the conditions for the Antichrist to come on the scene peaceably, with his seven-year "peace" contract confirmation, and it is this that begins the Tribulation.
Sin will not be taken away, only the deception will be gone. The small private sins are just as deadly as the big sins. The wages of sin is death and death is the only penalty given. If it were judged immediately, there would be no one left for the battle at the end of the Millennium.
The deception of Satan will not be there, however men will still be born on this earth with their sin nature and will have to accept Christ to go into eternity. There will be sin that is judged by Christ:
And he shall judge among many people, and rebuke strong nations afar off; and they shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up a sword against nation, neither shall they learn war any more." (Micah 4:3)
Behold, the days come, saith the LORD, that I will raise unto David a righteous Branch, and a King shall reign and prosper, and shall execute judgment and justice in the earth. In his days Judah shall be saved, and Israel shall dwell safely: and this is his name whereby he shall be called, THE LORD OUR RIGHTEOUSNESS" (Jeremiah 5:5,6)
So Christ will judge sin, and there will also be death:
No longer will there be in it an infant who lives but a few days, or an old man who does not live out his days; for the youth will die at the age of one hundred and the one who does not reach the age of one hundred Will be thought accursed. (Isaiah 65:20-25)