Enos uses the standard phrase “began to be old” to indicate that he is about to die. He declared that one hundred and seventy-nine years had passed from the time that Lehi had left Jerusalem. That dating is a question, and one without a clean answer. It is possible that there was a missing generation, but the record is otherwise consistent in listing those caring for the record, such as in the book of Omni, where multiple record-keepers do little more than indicate that they were in the line to do so. We also have the problem of knowing that Jacob’s son was named Enos and was charged with the records (Jacob 7:27). There is really no textual room for a missing generation, even if there is time.
The most likely answer is that Enos was born much later in Jacob’s life, and that both Jacob and Enos lived to be seventy or eighty. That is still an extended chronology, but possible.
Note that as Enos leaves his final blessing, he returns to the theme of his wrestle before Jehovah to receive forgiveness. Enos says that he must “declare the word according to the truth which is in Christ.” That was what he learned that allowed his sins to be forgiven, and it was the most important message of the Nephite prophets.
The phrase “when my mortal shall put on immortality” echoes the language of 1 Corinthians 15:53. Obviously it could not have been a reference to that verse, and, therefore, the language similarity is the result of the translator’s choice of words. The plates were not in English, so that phrase could not have been on them, even though the concept could have been.