Perhaps it would be best if you did some study on the Hebrew text and the meanings of the words found there. I have done this because the translators have not concisely or accurately conveyed the context of the Hebrew text into their English translations.
Gen 15:18-21 is the description the land that they will possess for a time so that they can know that God's Promise of the whole earth will become a reality in the distant future as Daniel wrote in
Daniel 7:26-27: -
26 ‘ But the court shall be seated,
And they shall take away his dominion,
To consume and destroy it forever.
27 Then the kingdom and dominion,
And the greatness of the kingdoms under the whole heaven,
Shall be given to the people, the saints of the Most High.
His kingdom is an everlasting kingdom,
And all dominions shall serve and obey Him.’
and in Daniel 12: - 1-4: -
12:1 “At that time Michael shall stand up,
The great prince who stands watch over the sons of your people;
And there shall be a time of trouble,
Such as never was since there was a nation,
Even to that time.
And at that time your people shall be delivered,
Every one who is found written in the book.
2 And many of those who sleep in the dust of the earth shall awake,
Some to everlasting life,
Some to shame and everlasting contempt.
3 Those who are wise shall shine
Like the brightness of the firmament,
And those who turn many to righteousness
Like the stars forever and ever.
4 “But you, Daniel, shut up the words, and seal the book until the time of the end; many shall run to and fro, and knowledge shall increase.”
Notice that at the end of time when the Israelites are delivered that the land has no real part in whether they receive everlasting Lift or everlasting contempt.
Your fixation on a Promised Land plays little part in the outcome as described by Daniel.
As for the Genesis 17:7-8 passage that you have also quoted, after consulting an interlinear I would paraphrase these two verses in this way: -
7 And I will establish My covenant between Me and you and your descendants after you in their ages, a covenant that will last until the vanishing point of time in this time period occurs, for the purpose of being God to you and your descendants after you. 8 Also I give this entity, to your descendants after you, the country in which you are a stranger, all the country of Canaan, for a long period of time {where the vanishing point for this time period is in the {distant} future} as a possession; and I will be their God."
Now if we consider the promise that God would give Abraham's descendants the country of Canaan as a possession, this was fulfilled when Joshua lead Israel over the river Jordan into the Land of Canaan to possess it. However, because of Israel's continual idolatrous worship God also told Israel that if they continued with their idolatrous worship that He would remove them from the land of Canaan and scatter them throughout the whole earth and that they would be trampled upon wherever they were found to be living until they repented and turned once more back to God. Again, the "Promised Land" does not figure in this redemption. Only their repentance of no longer wanting the have Satan as their King and master figures in their redemption.
Shalom