Referring to your teaching on Melchizedek, the Bible is not clear on when Shem died or how long he lived, is it? How do we know it was Shem and not Noah who was the "Melchizedek" who met Abram?
According to scripture, Shem lived 600 years:
According to v.11, Shem lived 500 years after he became the father of Arpachshad. This statement indicates that Shem died after the 500 years, therefore he died 502 years after the flood at the age of 600.
Furthermore, if we trace the births and deaths of the patriarchs in the seed line carefully, we find that Abraham was born 392 years after Shem. Since Abraham only lived 175 years, Shem outlived Abraham by another 32 years. Therefore, Shem must have been the Melchizedek of Abraham’s day, since he was the oldest living patriarch in the line of the seed promise when Abraham was alive.
We can’t know Shem’s age when he met Abraham, but it’s likely Shem would have been about 450 years old when he met Abraham.
Finally, there were 892 years between Noah’s birth and Abram’s birth. Since Noah lived 950 years, we know he died shortly before Abraham left Ur to go to Canaan (when Abram was 58). Once Noah died, Shem inherited the title of Melchizedek.
Our Genesis Bible Study may be helpful.