Jesus's historical existence does not mean all the miracles attributed to him are real or that all details of his story are true. The story on him was written long after he died and you make it sound like it's enough to justify everything claimed about the character. Furthermore in terms of proof most of the text written about him are written as if they were witnesses of the events when they're just recounting what others told them. See https://en.wikipedia.org/wiki/Q_source for more details.