The 7th Trumpet declares Jesus as King over every single nation.
Revelation 11:15 And the seventh angel sounded;
and there were great voices in heaven, saying, The kingdoms of this world are become
the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever.
We don't know who the great voices in heaven are in Revelation 11:15. Presumingly those of high ranking angels. In Revelation 11:16-18, the 24 elders chime in. Saying that God's wrath has come, and the time to reward the prophets and saint, small and great.
16
And the four and twenty elders, which sat before God on their seats, fell upon their faces, and worshipped God,
17 Saying, We give thee thanks, O Lord God Almighty, which art, and wast, and art to come; because thou hast taken to thee thy great power, and hast reigned.
18 And the nations were angry,
and thy wrath is come, and the time of the dead, that they should be judged, and that thou shouldest give reward unto thy servants the prophets, and to the saints, and them that fear thy name, small and great; and shouldest destroy them which destroy the earth.
The 3rd woe is if Satan is declared the 8th king over the entire world.
No, there is no such condition. The 3rd woe, without qualification, will be Satan cast down to earth having great wrath, knowing that he has on a time/times/half time left.
Revelation 12: Therefore rejoice,
ye heavens, and ye that dwell in them.
Woe to the inhabiters of the earth and of the sea! for the devil is come down unto you, having great wrath, because he knoweth that he hath but a short time.