Sure I would agree mostly or almost all anyway that the promises have been fulfilled. All of the bulk of prophecy has been fulfilled in order for the church to completely replace Israel (or what many dispensationalists call replacement theology). In thinking about Matthew 5:18, maybe I don't understand the passage as well as I thought. I mean is it literally saying that one jot or one tittle will pass from the law once all is fulfilled? I don't so. In the gospel of mark it drops the phrase "till all be fulfilled."
Mark 13:30-31
30 Verily I say unto you, that this generation shall not pass, till all these things be done.
31 Heaven and earth shall pass away: but my words shall not pass away.
Notice the difference in the wording. It's made more clear in how it's worded that he simply refers to his word as inerrant.
Matt. 24:34-35
34 Verily I say unto you, This generation shall not pass, till all these things be fulfilled.
35 Heaven and earth shall pass away, but my words shall not pass away.
Matt. 5:17-18
17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
I think it's simply saying that the purpose of scripture is to be fulfilled and it is more reliable than the earth or the heavens. The "law and the prophets" is another way of referring to all the Old Testament and the Old Testament is not the same thing as the old covenant.
Lastly, is he really saying every last prophecy needs to be fulfilled in 70 AD in order for the old world to pass away? Or is it that every relevant prophecy which is the bulk of prophecy needs to be fulfilled? The Pharisees believed in the resurrection of the body yet Jesus or the apostles never bothered to correct them on it.
Jesus is not speaking of the literal cosmos he is speaking of the Mosaic age and its Temple. Temples often contained images and symbols representing both the heaven and the earth including the Tabernacle, Solomon's Temple, and Herod's Temple. Temples were a microcosm of creation itself and in fact the Holiest of Holies was a typology / shadow of Kingdom of Heaven itself.
HEAVEN AND EARTH HAVE ALREADY PASSED AWAY
The Bible often speaks of the heavens and earth in its literal sense as in Genesis 1:1, but it also uses these terms metaphorically, figuratively. It is this second use that we will examine in this paper.
1. Two main ages Generally speaking, first century Jews had the conception of two ages—the Mosaic Age and the Messianic Age— also called the Old Covenant and New Covenant. (Jer. 31:31f). Because the New Testament writers lived before the definitive end of the Mosaic Covenant in AD 70, they describe the two ages as “this age” (Mosaic) and “the age to come” (Messianic, Christian, Kingdom of God). The latter is the New Heaven and New Earth.
2. In Hebrew thought, “Heavens and Earth” were figurative for the political/social/religious order of a people.
A. This prophecy concerning the coming destruction of Babylon by the Medes, was stated in terms of destroying their heaven and earth. “Therefore I will make the heavens tremble, and the earth will be shaken out of its place in the wrath of Yahweh of Armies, and in the day of his fierce anger.”Is. 13:13
B. In this scripture, God is outraged with Israel’s rebellion and waywardness. “Hear, heavens, and listen, earth; for Yahweh has spoken: ‘I have nourished and brought up children, and they have rebelled against me.’” Is. 1:2
C. Prophecy: Yahweh’s special “heavens and earth” will rejoice at the destruction of Babylon. “Then the heavens and the earth, and all that is therein, shall sing for joy over Babylon; for the destroyers shall come to her from the north, says Yahweh.” Jer. 51:48
3. God created a covenantal “heavens and earth” when he chose Israel to be His people. Here Isaiah reminds the Jews of the special protective relationship they enjoy with Yahweh. “I have put my words in your mouth, and have covered you in the shadow of my hand, that I may plant the heavens, and lay the foundations of the earth, and tell Zion, 'You are my people.'" Is 51:16
4. Jesus prophesied that the old “heaven and earth” would pass when every bit of the law and prophets was accomplished. This was the passing of the Old Covenant which signaled the beginning of the New. "Don't think that I came to destroy the law or the prophets. I didn't come to destroy, but to fulfill. For most certainly, I tell you, until heaven and earth pass away, not even one smallest letter or one tiny pen stroke shall in any way pass away from the law, until all things are accomplished.” Mt. 5: 17.
5. Jesus prophesied that His generation would see the end of the old "heaven and earth”. “Most certainly I tell you, this generation will not pass away, until all these things are accomplished. Heaven and earth will pass away, but my words will not pass away.” Mt. 24:34-35.
6. Yahweh promised a “new heavens and earth” after the Mosaic “heavens and earth" passed. "For, behold, I create new heavens and a new earth; and the former things shall not be remembered, nor come into mind.” Is 65: 17
7. In his vision, John saw the new “heaven and earth” replace the old Mosaic “heaven and earth”. “I saw a new heaven and a new earth: for the first heaven and the first earth have passed away…” Rev. 21:1
8. Peter welcomed the destruction of the Old Covenant and installation of the New Covenant. “But the heavens that now are, and the earth, by the same word have been stored up for fire, being reserved against the day of judgment and destruction of ungodly men…But, according to his promise, we look for new heavens and a new earth, in which righteousness dwells.” 2 Peter 3:7, 13
9. What does history report regarding the old “heavens and earth”? The temple was destroyed by fire in 70 AD. The records of priestly succession were also destroyed annulling any reconstitution of the Aaronic Priesthood. Without a temple, priesthood, altar, records, etc. there were no traces of the first Mosaic heaven and earth left by the winter of AD 70.