First, Physics Guy, let me clarify the syntax of my sentence:
As for the "weak" case for a historical Jesus, there is nothing on offer with more plausibility, and it is only weak in relation to something else: it is weak in relation to case for the historical existence of Franklin Roosevelt, still weaker than historical Caesar and Alexander, but not weak in comparison to a historical Odysseus or a historical Nephi.
To me it seems clear that "it" (pronoun = "case for historical Jesus") is the subject of the first term of the series and is implicitly the subject of the remaining terms, since no other subject is expressed. I could have (should have?) written it this way:
The case for historical Jesus is weak in relation to the case for the historical existence of Franklin Roosevelt, and the case for historical Jesus is still weaker than the case for historical Caesar and Alexander, but the case for historical Jesus is not weak in comparison to a historical Odysseus or a historical Nephi.
I'm sorry I gave the impression that I was saying the case for Caesar's existence is greater than that of FDR, though I honestly don't know how I gave that impression. I don't drink kool-aid, and never have, but I've frankly never heard of anyone who thought we know more about Caesar than FDR, and I'm kind of surprised you could think a person who was able to write anything I've ever written in this forum could be capable of asserting such an absurdity.
In a sense, you've kind of given me an example to answer your first concern: of course people can wildly misread an author, and of course an author can write so that s/he is wildly misread. And that is the kind of issue you find in comparing manuscripts. Outright forgeries of the kind "too good to be true" aren't that common, and when they are, they are vigorously contested with a lot more than just a mere hunch, which is all that "too good to be true" really is. Go ahead and claim that Caesar wasn't murdered in the way all of our sources say: the burden is on you (not to be misunderstood: the general "you," not you personally) to explain 1) what actually happened and 2) how the wrong information came about and was perpetuated.
Moreover, there are several examples of texts whose manuscript history extends close a 1,000 years (Vergil, for example), and the variations are minor: places where Virgil was misunderstood, scribes tried to correct, for example. Or take Homer's Iliad, the earliest manuscript of which is 9th century. Beginning in the 19th century, lo and behold papyri from hundreds of years earlier were unearthed from Egyptian sand and we can actually trace the accuracy of the 9th century manuscript. It turns out to be quite stable. Same goes for the Bible, the earliest manuscript of which were from 10th century until the discovery of the Dead Sea scrolls. There are some interesting cases of deviation (shorter Jeremiah, but we already knew about that from the Septuagint), but on the whole the text seems to have been very stable over exactly that 1,000 year span. This holds true even in the case of orally transmitted texts. The oldest manuscripts of the Rig Veda, for instance, are from the 11th century AD, but the linguistic evidence shows irrefutably that vast portions of that text are essentially unchanged from at least the 13 century BC—24 centuries. Nor should this be surprising if you look at the subcultures whose job it was to maintain the tradition. In India, for example, there were entire families who memorized sections of the Rig Veda backwards, and anytime there was a question about the accuracy of the text, their version was compared to the those who had memorized it forwards. Obviously, for that former group, the reverse Rig Veda was nonsense and was valuable precisely because the later dialect of Sanskrit couldn't interfere. And the Leningrad Codex of the Hebrew Bible was maintained by a family of scribes—real professionals, I'm talking about, not just people "trying to do the best they can"—who counted ever letter, then counted every paragraph, then counted every section and left their tallies in the notes and manuscripts so later scribes in the family could check. So, what do you (general "you") think the monks doing all that copying were doing? They were highly trained professionals who knew what they were doing, and the result is that it is extremely rare to find any serious deviation in manuscripts. The fact that it was a process over a 1,000 years and more is irrelevant, and anyone who is going to brush away the thousands of cumulative man-years and man-power that went into all that had better know what they're talking about.
"As to any slivers of light or any particles of darkness of the past, we forget about them."
—B. Redd McConkie