With regard to the concept of hell and Greek understanding, while we know that all Scripture is given by inspiration of the Holy Spirit, The “all Scripture” that is being referred to is the Hebrew Scripture. The King James Version was written by using the Septuagint (Hebrew to Greek translation), converting the Greek into English. Thus, the resulting English translation carries Greek interpretation, which is where the problem lies. A direct Hebrew to Greek translation is what would be needed to fully grasp the Hebraic understanding of the text.
I completely agree with you. It would not be ideal to translate into English from the Greek Septuagint, which would be a translation of a translation. It is also true that in the primitive Christian church–the churches as well as the leaders who wrote to them–used the Septuagint translation. Obviously, that is what they did, because they spoke Greek. If I were to quote the Bible to you right now, I would use an English translation, because neither you nor I speak Hebrew. You and I read a translation and we teach from a translation.
However, the problem you describe is simply not a problem for us today. Here is why. Modern translators of the Old Testament translate from the Hebrew, not the Greek. If you look at the notes in the bottom of your Bible, you may find an occasional reference to the Septuagint. This is because when translators do their work, although they start primarily from the Hebrew text, they do also consider the Septuagint, and even occasionally allow their decision to reflect the Septuagint. However, in nearly every case, the Hebrew text is the one used to make the basic translation. I guarantee you that the English Bible you use was translated from the Hebrew, not from the Greek Septuagint.
On a side note, you claim that the King James version was created by translating the Septuagint. That is not correct. The first modern translation into English was that of Tyndale. He, like the committee that created the King James, used the Masoretic Hebrew text, not the Septuagint, as the main source for the translation. Tyndale was a Hebrew scholar.
By the way, one example to illustrate that scholars do at least occasionally use the Septuagint to help understand the Hebrew is Isaiah 7:14. This is the passage which is a prophecy that the Messiah will come from a virgin. The Hebrew of Isaiah 7:14 is a word which means “young woman.” The word can be for a virgin or possibly for a very young woman who happens to be married. If we did not have the Septuagint, perhaps some, but not all translations of Isaiah 7:14 would be “Behold, the woman will be with child.” However, it is useful to note that the Septuagint Greek translation of Isaiah 7:14 is a Greek word which unambiguously means virgin–ie. a woman who is not yet married and is still a virgin. What this proves is that the Jews in the third century BC who translated the Hebrew to Greek understood the implication of the Hebrew word to be a virgin, not simply a young woman. The Septuagint offers useful insight into the Hebrew understanding of their own words, as it tells us how a Jewish person understood the Hebrew word when the Septuagint translation was made in the third century BC.
So, it would not be quite as bad as you might think to translate into English from the Septuagint/Greek version of the Old Testament. Nevertheless, you can be sure that your English Bible comes from the Hebrew text, more specifically the Masoretic Hebrew text, working together with the Hebrew Dead Sea Scrolls.