My bold.
We've been here before, haven't we?
You have been shown how Historians evaluate this question, but you find their methods inadequate. You keep asking for: "credible evidence at all of Jesus as a living person ever known to anyone". I'm not sure what such evidence would look like:
- An ancient document by someone saying "I knew Jesus"? That would be no more evidential than the gospels.
- A portrait painted from life? Again, no way to verify such a thing.
- A statue?
- A gravestone?
None of those things could ever be totally "credible".
Please explain what you would consider: "credible evidence at all of Jesus as a living person ever known to anyone".
What do you expect from ancient Historians?
Well, in all fairness, a lot of what's gets called "how historians do it" in relation to Jesus is really the completely different topic of "how Bible Studies does it." Some of them do come close enough to the modern historical method, except when it's about the existence of Jesus. (E.g., Ehrman.) A few seem still stuck in the 19'th century or so, as historical methods go. And a lot are in between.
The very short version is that while, yes, any of the things you listed can be fake, that's just the reason why we want more than one, corroborating each other, but being independent of each other. As Ehrman aptly puts it, if you have 20 accounts of something, but they all copied from the same guy, you don't have 20 sources, you only have one.
We also like sources to be mentioned, preferably even quoted, by other sources. Among other things, because it shows that the latter source actually existed at the time.
We also like sources to be unbiased, not propaganda material. Well, that's rarely available, but having sources with different agendas or attitudes corroborate something is the next best thing. If Plato really likes Socrates and promotes him as an example, while Aristophanes takes the piss out of Socrates in "The Clouds", but both confirm that he did X or said Y, then it's less probable that they both made the same thing up to further their very conflicting agendas.
We also REALLY don't like oral transmission. In fact, there are some fairly hefty requirements in the modern historical method for it to not get promptly discarded. You have to be able to support stuff like that there are multiple independent oral traditions about that guy (which we don't really know for Jesus), and/or that he was basically a superstar that everyone knew and it limited how much BS you can make up about him.
So, yes, if you just have Plato telling you about the great arguments of the great philosopher Timaeus in his talks to Socrates, but nobody else seems to have even heard of such a great philosopher, not even other students of Socrates (e.g., Xenophon) who should have been interested in those arguments, then Timaeus probably never existed. But if we were to find some new document from that era, preferably arguing AGAINST the same teachings of Timaeus, then we'd almost certainly go with Timaeus being very real.
So, short version, it's not that there's anything wrong with any of the kinds of evidence you mentioned, but basically yeah, alone and on their own any single one of them wouldn't do much about any historical character. You'd want to have SOME corroboration.
We also REALLY like the criterion of historical necessity, among other criteria. Which is really just Occam for historians. Basically you'd want to have SOME evidence that NEEDS those extra entities to explain that evidence. E.g., if you dig up a lot of skeletons and arrow heads in some location, you pretty much NEED someone to have lead an army and had a battle there.
But if it's just Plato using Timaeus to promote his own ideas, or Paul writing about Jesus, then you don't really need a Timaeus or a Jesus to explain those. You need someone who wrote the dialogues or the epistles, but you don't need a historical character to explain how an author created a character. We need a historical Plato who wrote the dialogues, because the dialogues didn't just materialize out of thin air, but we don't need a historical Timaeus to explain how Socrates could come up with a character like Timaeus. We know that people are perfectly able to make up characters for their stories.
Etc.