It sounds like you are following the theories based on the historical war acts of Antiochus from the Daniel 11 chapter, and theories by those like Hal Lindsey and Chuck Missler.
Rev 13:4-8
4 And they worshipped the dragon which gave power unto the beast: and they worshipped the beast, saying, "Who is like unto the beast? who is able to make war with him?"
5 And there was given unto him a mouth speaking great things and blasphemies; and power was given unto him to continue forty and two months.
6 And he opened his mouth in blasphemy against God, to blaspheme his name, and his tabernacle, and them that dwell in heaven.
7 And it was given unto him to make war with the saints, and to overcome them: and power was given him over all kindreds, and tongues, and nations.
8 And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
KJV
The end of this world with the coming Antichrist is going to be different. Those nations which tried to make war historically with Antiochus will instead be bowing in worship to the Antichrist. That above Scripture verifies this for that 42 months, which is the great tribulation period.
Christ's Church isn't going anywhere during that period. The Church is not gathered until Jesus comes to do battle at Armageddon on the 7th Vial, which is also when the "day of the Lord" events happen. This is why our Lord Jesus was still warning His Church on the 6th Vial in the Rev.16:15 verse that He comes "as a thief".
The "For without" phrase in Rev.22:15 does mean exactly that the wicked are outside the gates of the holy city in that time. They are in the place of separation Jesus warned about in The Gospel, i.e., the "outer darkness". That is not the lake of fire; it is a place of separation outside the gates of the city. It is where the nations of unsaved are during Christ's thousand years reign.
The Ezekiel sanctuary layout covers a much larger area in the middle east than any other previous time. So we cannot say the wicked outside the gates will be able to have access to the tree of life. The Rev.22:14 verse suggests they won't have access to it, as what would be the need to even mention who has right to it if the wicked were already gone?
Rev 22:14
14 Blessed are they that do His commandments, that they may have right to the tree of life, and may enter in through the gates into the city.
KJV
Furthermore, per Ezekiel 47, the River emits out from under God's House, the millennial sanctuary. That is the temple of Rev.7:14-15; it is on earth after Christ's return, which is when that Rev.7:14-17 Scripture begins, and notice the last verse there...
Rev 7:17
17 For the Lamb Which is in the midst of the throne shall feed them, and shall lead them unto living fountains of waters: and God shall wipe away all tears from their eyes.
KJV
Just that River being associated with that temple or sanctuary in that time is proof enough that is the Millennial time, and not the new heavens and a new earth timing, because Rev.21:22 says there is no more temple with the new heavens and new earth timing.
The literal manifesting of God's River on earth should not be a surprise to Christ's Church, because it was first shown on earth in Genesis 2:10-14 along with God's Garden of Eden. God's River was even shown flowing out of His Eden to feed four other rivers upon the earth, two of which we still know their location today, the Euphrates and the Hiddikel or Tigris:
