Some of the Masoretic edits are really crafty. There’s the popular ones like changing “they pierced my hands and feet”, but a subtle one that sticks out to me is Genesis 11, when it lists the genealogies of Shem and so on. After Shem, lifespans change dramatically. Instead of the usual long lifespans, they cut in half. It produces the crazy effect of Shem (the last long lived patriarch) to actually outlive his great great great/etc grandsons! He lives all the way into Abraham’s era.
But in the Septuagint, the lifespans are much longer. Completely different! Shem doesn’t outlive any of them.
Now here’s the kicker: The Jews have a tradition of saying Shem is actually Melchizedek, and this is how he befriended Abraham. To this day they teach this. Why?
Look at Hebrews: It calls Jesus a priest in the order of Melchizedek, “having no father”… a mysterious figure. And it argues that Jesus is worthy to be a High Priest, because he’s part of this order of Melchizedek. It’s unthinkable for a Jew to be a Priest unless they are Levites. But Hebrews argues that Melchizedek is a higher priest than Levi, because he predated him and even blessed Abraham (where Levi was in his loins).
So the Jews altered the text in Genesis and made Melchizedek into Shem, and part of the same branch of Levi… and hence, this negates the High Priesthood of Jesus.
And this is just one thing you’re going to have to work with. They had millennia to build this up.