So if it would turn out that Jesus had never existed, then the entire chain of belief would shatter and fall apart like a castle of cards.
Not really, I defend Christian values and principles even without the existence of any kind of deity.
I will not refute the whole matter you are discussing, because evidently, as you say, there is almost no proof, or there is no proof whatsoever, that this happened, however, I consider several things.
I believe that people generally misinterpret the Bible, since they lack historical context to understand it, interpret words, sentences and paragraphs, many times, giving current connotations to it.
Anti-Semitism, yes it is true, was justified many times for the reason you describe, the reality is that this has always been the farce, the Jews have caused problems in almost every place where they have arrived. The hatred and confrontation between Jews and Christians have been mutual, they have to leave victimhood, they never integrate into Christian societies, and they always have a disproportionate over representation in positions of influence.
By the way, it must be very rational to think "in being the people chosen by God", what kind of rationality is that? I wonder if the Jews abandoned that belief when it comes to governing, which is what they do, just as a Christian has to abandon his belief in order to be an engineer, as you say.
See that is exactly the type of anti-semitism I have been describing. What kind of "problems" are you referring too that weren't just pure fabrications of the Church and anti-semites within?
I have wrote a lenghty post debunking anti-semitism, turns out 80% or more of anti-semitic concepts came from ultra-religious christians: