You asked about the Christ Event
You asked about the Christ Event. It's familiar theological shorthand or jargon and refers to the fullness and completion of salvation in Jesus' birth, life, death, resurrection and ascension. "Event" emphasizes Christianity’s claim that God acts most definitely and most definitively within the context of human history, and so emphasizes that our salvation's not just a vague religious generality but actually something quite un-religious, very un-otherworldly: God's invasion into the course of human history in order to fulfill all of his promises, in order to draw creation back to its Creator, all of this occurring in an actual "event" that happened within definable linear, chronological time and at a specific longitude and latitude, on a stage filled with human actors. You know...like "wind event," "terrorist event," cardiac event"...I hope this helps!
"Jesus is 'myth'?" Gerhard von Rad points out that myth has a greater degree of density than history. I'd assume density makes myth truer than history, at least in some sense. But I also know Jesus was a human person, like you and me, one who lived and walked etc., on this earth in the course of human history – whatever meaning you choose to assign to that. And as Holy Spirit, Jesus does live within us, but (in my humble orthodoxy!) I also meet Jesus again and again not only in the scriptures as the "unique and authoritative witness to God's activity and God's word to me" ("divine revelation, human disclosure" again); I also meet Jesus as the Spirit indwelling me and I meet Christ Jesus in others, whether or not they specifically define themselves as Christians or as Jesus people of some kind or another.
What I'm saying here is I have a serious problem with your use of the word "myth," though clearly there's a whole lot about Jesus that's far larger-than-life, at least larger than life as I commonly experience it. In The God of Jesus, Stephen Patterson says Paul's Jesus gradually assumes gigantic (otherworldly?) mythic proportions.