Israel was set aside in Ac 28:28, for unbelief, when the Salvation of God (Jesus Christ) was taken from them and given to the Gentiles. They became Loammi, Not My People, as in Hosea 1:9. Hosea 3:4 shows their present condition. Hosea 6:2 says they will be back after 2 days, 2000 years. The 2000 years will be up about 2064. When Israel was set aside, EVERYTHING associated with Israel was set aside, This means that everything contained in the 59, all-Israel books, except for Christ, was also set aside, as far as it being TO us or ABOUT us is concerned. The ONLY books TO us and ABOUT us today, are Paul's 7 post-Acts books (see below). With study, it's simple to see that Paul's last 7 books have NOTHING in common with the other 59, 100% Israel books, except Christ, of course.
With no Israel, Christ revealed to Paul the Dispensation of the Mystery, Ephesians 3:3, which had been hid in God since the world began, and way before Israel existed, Ephesians 3:9, Colossians 1:26. The only place today's Truth is found is in Paul's last 7 epistles, all written after Acts. In them a brand new church is established, which has a Hope of being resurrected into the Heavenly Places, where Christ sits at the right hand of God, Ephesians 1:20, Ephesians1:26. No one in the other 59 books EVER had a chance of going to Heaven. They had the New Jerusalem, at best. The NJ isn't Heaven. It comes down out of Heaven and attaches to the New Earth. Each tribe has it's own gate. There is no Gentile gate.
Everything that Paul wrote during Acts was based on the OT, Acts of the apostles 26:22. Everything after Acts was written way before any of the OT was written. Therefore, it is impossible that anything in those other 59 books, including Paul's Acts epistles, have ANY part in Paul's post-Acts epistles. It's not possible to merge ANYTHING, except Christ, from these 59 Jewish books, with Paul's 7 post-Acts.
I don't know where Paul mentioned the Sermon on the Mount in his Acts epistles. It makes no difference, since I am positive it wasn't in his last 7 epistles, the ONLY books written TO and ABOUT us Gentiles, today. The other 59 all-Israel books are invaluable FOR our learning, but there is nothing in them about our Hope, Calling, or our future
Knowing all this, my main thing, dispensationally, is to keep everything Israel (except Christ), or Jewish, out of my doctrine. God, in EVERY case, has treated Israel (Jews) totally different than he has treated Gentiles. If one believes both the Israel things and the Gentile things are given to him, there will be many contradictions, and self-inflicted contradictions always set up a pick-and-choose situation, which is never acceptable. To combat this, God introduced the concept of rightly dividing (make a straight cut; Correcting Cut) God's Word, 2Tim 2:15. It doesn't say WHERE scripture must be cut and divided, but, since the verse appears only in Paul's post-Acts epistles, where Israel plays NO PART AT ALL, it is obvious that God wants us to cut it in a place where it is 100% Israel on one side of the cut and 100% Gentile on the other side. The only place possible is between Acts and Ephesians. If we do this correctly, we are approved unto God and have no need to feel ashamed, 2Tim 2:15.
I know you feel differently, but I am totally convinced, with ZERO doubts, that ANYTHING that Christ taught the 12, the multitude, or the Pharisees, during His 3-1/2 year earthly ministry, is absolutely NOT TO or About anyone living today. My proofs are Matthew 10:5 , Matthew 15:24 , Romans 15:8 , and John 1:31.