To begin with your fourth comment, I have italicized all scriptures I post for the sake of separating God's words from my own which are not italicized. It's just something I do as a form of habit. So, I think there is just a misunderstanding here regarding my use and purpose of italics.
Your initial remark is also a misunderstanding of what I said. I never said that I have read the original written parchments. I said that I don't need to. As many times as the original parchments were re-copied, I can be sure that God preserved his word pure forever as I stated with Psalm 12:6-7. It's his original words that he promised to preserve and not any translation. That is why each translation is translated from another source and not just written with words that came to the translators by inspiration of God. No, God already gave his word by inspiration in the Hebrew and Aramaic and Greek. You can doubt the validity of the received text based on what history books tell you, but I have no reason to doubt that God is the one who preserves his word.
In your first point, you have provided no scripture to demonstrate that a plural word is allowed to be translated as a singular word without ample biblical support. What you are doing is using basic "rules of grammar" (common sense) which doesn't go very far when it comes to the spiritual word of God. The translators came across the plural word "Sabaton" and let's just say that they had the same reasoning you stated above for doing so. That, "While the English word” week” is singular, however, it carries plurality being equivalent to 7 days.". What you are suggesting is inconsistent with the scriptures. If God wanted a word to be singular, he would have written it as such and vice versa. I provided Galatians 3:16 as my example which you did not take into consideration in your comments, but instead relied on rules of grammar to explain the mistake that has been made by the translators.
But this was not the only place where this mistake was made regarding the word "Sabbath". We can take a look at a few more.
Matthew 12:1 (KJV 1900)
At that time Jesus went on the sabbath day through the corn; and his disciples were an hungred, and began to pluck the ears of corn, and to eat.
Please look in your interlinear (which is the original Greek text of the Word of God, for those who are following along and may not know) and take a look at the word that was translated as "sabbath". You'll notice that this word is also plural in the original text. Yet the translators decided to translate it as a singular word, but not only did they do that, but they also added the word "day" into the text and did not italicize it like they should have to let us know that this word is found nowhere in the original text. So, as this verse read in the KJV, it seems to indicate that Jesus only did this on one occasion, when in fact, he did this on multiple Sabbaths.
Matthew 12:1 (KJV 1900)
At that time Jesus went on the SABBATHS through the corn; and his disciples were an hungred, and began to pluck the ears of corn, and to eat.
Do you see how a correction in the translation can drastically change the meaning of a passage? I hope so. Let's take alook at another.
Luke 18:12 (KJV 1900)
I fast twice in the week, I give tithes of all that I possess.
Here the translators came across the singular word for Sabbath and translated it as "week" (which is also singular). This shows an inconsistency in their translation, to use the word "week" whether they come across a singular or plural word in the original text. Nevertheless, had they properly translated it as "Sabbath", it teaches us that this Pharisee didn't say that he fasted 2 times in a 7 day period, but 2 times in the same day. And per the context, this would be a better understanding anyway, as he was trying to distinguish himself above his neighbor by his great sacrifice of fasting and many works.
Incidentally, the Greek word for "Sabbath" comes from the Hebrew word for "sabbath", so the rules of grammar you initially pointed out fall extremely short because the Hebrew word for "Sabbath" is not the same word for "seven" or for "week", they are all individual words. This is why our reasoning must be from the scriptures alone. This is one cohesive book from the mouth of God. The Hebrew word for "Sabbath" is only translated as "Sabbath" and the Hebrew word for "seven" and for "week" are never translated as "Sabbath". Therefore we can (with plenty of biblical support) say that if God wanted to write the word "week" in the New Testament, he would have done so. Likewise for the word "seven".
But when we let ourselves be led by what the inspired word of God declares, then we can arrive at correct biblical truths.
Your second comment is not relevant because you are assuming that the Greek word "“heis” is in the original text, but it is not. The translators even italicized it to make sure we didn't think it was.
And your third point, again, is faulty because you're placing grammatical rules over what the text is actually showing you it says. I don't know if you're doing this because you believe the KJV is infallible or what other reason. But to say, "the English has “in the end” pointing to a certain day not days hence, the Sabbath and not “Sabbaths”. By the way, the English word “Sabbath” has been translated in the KJB correctly and it is not necessary to change it to “SABBATHS”".
The word "end" can point to a day or days. It all depends on what God has written, right? And he has written that it's pointing to the end of SABBATHS. Therefore your determination that it need not be changed is done so without any biblical scriptural support. That is what we would all like to see here, this way we have something to compare to in order to make sure that what you're saying is so (Acts 17:11).
God made them both plural in Matthew 28:1, therefore, our job is not to side with the translators as "inspired men", and then try to come up with grammatical way to rationalize what they have done, but instead to ask, "why did God write it this way in his original word?". When you assume/believe that any translation is inspired and thus infallible, then you will never question it, and that is a huge mistake.