... you have no way of showing that any statements attributed to Jesus aren't mistakes, exaggeration or lies for the purposes of propaganda: since these are known risks involving human artifice you'd need to exclude these, and if you can't then you could be dealing with retrospective prophecy
Two things. Firstly, the people who were the source of the gospels (the Twelve, the women and various other witnesses described. Paul too, for that matter) allowed their weaknesses to be exposed by the authors (the evangelists) thus had no regard for their reputation.
Secondly, we are told all but one (John) of the twelve died in horrific ways rather than denounce Jesus. And the first generation of Christians was fed to lions, burned alive etc.
So no retrospective prophecy, imo