Yeah, I don't know if any argument would be able to change your mind if this is the standard that you have, which is a reasonable one I would say.
Christians usually believe in "interna; evidence", which is to say that the content of the gospels themselves are enough for someone to consider them factual rather than hear-say or corrupted information. I would have a hard time believing a non-christian scholar would ever entertain such a train of thought.
Nevertheless, I think some Christians, probably most would argue that the truth was preserved, and view the gap you're thinking of as pretty insignificant in comparison to the amount of time humanity has had access to biblical texts. This is meaningless iff you're not willing to have faith in the content of the document, obviously.
>there's no archaeological evidence to support it.
I think, ultimately, there is no way to prove the meaningful things of Christianity. If the text mentions Jerusalem, or the Sea of Galilee or a particular building, so what, who gives a shit? Anyone alive then would have known these existed, it doesn't lend validity to the supernatural claims. To accept that a God exists and that this God became a man and then died, but resurrected; to accept this as a thing that happened regardless of any documentation or the accuracy of its dating or anything like that, will always be either a logical leap or an exerciser in mysticism (whatever you'd like to call it). Faith.
I don't think, from what you're saying, that having these things be signed by random men, having more names for witnesses, having the manuscripts be earlier or having some more archaeological evidence would really do that much for you. I think you want proof of miracles and magic, which is something that I don't believe you will ever get. No one can prove Jesus was God, or that he was resurrected, or that God even exists.