You have claimed that because the oldest copy of the book of Isaiah dates to about 200 BCE (The Great Isaiah Scroll) that this is the only real evidence we have of Isaiah's prophecy. But there appears to be universal agreement that the Great Isaiah Scroll is not the original. The Great Isaiah scroll is a copy, and the process and methods employed by scribes in copying holy texts is cemented in tradition.
The Great Isaiah scroll is almost certainly not original, correct. The point is, we no longer have the original. Therefore, we do not actually know what the original said. Despite the methods used by scribes to copy texts in antiquity, we have numerous Biblical examples of cases wherein they did in fact make mistakes, and even intentionally added to or changed the text they were copying. This is plainly evident, for example, from the differences between the Masoretic Text and the Dead Sea Scrolls.
The materials used were of high quality, making the scrolls expensive, and the rules governing the copying of holy text were strictly followed to avoid mistakes. It is, therefore, highly unlikely that the book of Isaiah changed over the intervening 500 years (from Isaiah's time, about 700 BCE). Given the quality of these sacred scrolls, it is, actually, quite likely that the Great Isaiah Scroll was a direct copy of Isaiah's original.
[The Great Isaiah Scroll and the Masoretic Text | AHRC]
As even your own source points out, there are many differences between the DSS and the MT. This indicates that your belief that copyists would not make mistakes (or intentional edits) in transmission is simply inaccurate.
You also have no basis for the claim that it is "highly likely" that the Great Isaiah Scroll was a first generation copy of the original text. For one thing, scholars are widely agreed that all of what is now in the book of Isaiah was likely written by multiple people over time and added to the original. So in fact it is extremely unlikely that the Great Isaiah scroll is a 1st generation copy.
With regard to the issue of love, what do you think is the greatest thing a man can do for his fellow human beings?
I don't think there is one single answer to that question. It's extremely context dependent. You are likely to say that dying for others is the greatest thing a person could do, since that's what Jesus allegedly did. But of course if we all did that, none of us would be left to die for!