How long of a period of time does Revelation 14 cover?

Revelation 14:6 And I saw another angel fly in the midst of heaven, having the everlasting gospel to preach unto them that dwell on the earth, and to every nation, and kindred, and tongue, and people,
7 Saying with a loud voice, Fear God, and give glory to him; for the hour of his judgment is come: and worship him that made heaven, and earth, and the sea, and the fountains of waters.

There is the gospel in line 6, and also the warning in lines 9-11:

Revelation 14:9 And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand,

10 The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb:

11 And the smoke of their torment ascendeth up for ever and ever: and they have no rest day nor night, who worship the beast and his image, and whosoever receiveth the mark of his name.

Maybe the gospel in line 6, and the warning in lines 9-11, occur earlier in the tribulation, but isn't the trodding of the winepress at the second coming?

Revelation 14:1 And I looked, and, lo, a Lamb stood on the mount Sion, and with him an hundred forty and four thousand, having his Father’s name written in their foreheads.

3 And they sung as it were a new song before the throne, and before the four beasts, and the elders: and no man could learn that song but the hundred and forty and four thousand, which were redeemed from the earth.

5 And in their mouth was found no guile: for they are without fault before the throne of God.

Isn't mount Sion, in line 1, in heaven, since Jesus wouldn't be on earth before the second coming?

Then do not lines 3 & 5 show that they are before the throne, which is in heaven?
I had always been taught that the everlasting gospel, that the angel preaches in line 6, must only be what line 7 mentions that he said:

Revelation 14:7 Saying with a loud voice, Fear God, and give glory to him; for the hour of his judgment is come: and worship him that made heaven, and earth, and the sea, and the fountains of waters.

Is that really so?

Isn't it rather that line 7 is in "addition" to the gospel he preaches?

Line 7 doesn't sound like good news, does it?

Then what about the following line of scripture, given by inspiration of the Holy Ghost?

Galatians 1:8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.

If Revelation 14:7 is the gospel preached by the angel, then wouldn't he be in violation of Galatians 1:8 & accursed?

Also, do not, in the tribulation, people wash their robes in the blood of the Lamb, and overcome the devil by the blood of the Lamb?

But doesn't Revelation 14:7 mention nothing about the blood of the Lamb?

So, is it possible that the angel still preaches the death, burial, and resurrection of Jesus, even in the different dispensation of the tribulation?
Also, is it possible that the great saved multitude mentioned in Revelation 7:9, believed the gospel preached by the angel?

I had always been taught, and had always believed, that the 144,000 were all like the apostle Paul, and that's how those people got saved.

Do not both chapters 7 & 14 mention things about the 144,000?

But it never mentions that they also preach the gospel, do not we assume that they do?

Yet doesn't it say that the angel preaches the gospel?

Also, are not the four words used to describe those whom the angel preaches to,

the same used to describe the great multitude that was saved: people, nation, tongue, and kindred?

Revelation 7:9 After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands;

So is this even possible?