Jesus may not have built any temples, but He built a kingdom in the hearts of men that has changed History forever. The works of Seti are of historical interest only, save the tiny group you reference.
I'll admit You can't find the body of Jesus anywhere. That is not because He didn't exist, its because He STILL exists. We have proof Seti is not an actual God, it rests, as you say, in the Cario museum. We have no such proof concerning Jesus even though it was in the interests of the authorities of the day to take steps to ensure the body of Jesus was available as a museum piece.
The relationship between Judaism and Christianity is getting less clear all the time. In terms of language and images, Judaism might be a cousin to Babylon as is Islam, while Christianity would be an evolved form of Egyptian Mystery Religion. It might be a total accident that the new testament of Christianity is an appendix to the old testament. The Mystery Religions of Rome adopted Christianity with scarcely a burp, it was a smooth transition with little dislocation.
Or should we ignore the verbal ramblings of Paul the major player in early Christianity?
The ones who have studied the matter the most say that Christianity is a perversion of Judism, that Jesus was a rabbi but no messiah, and that the last supper with its lamb was a Passover meal. I don't know and care less.
The flood story and many of the other Biblical stories are stock items in Middle East myth. The Babylonians had a Noah-type hero called Gilgamish. One of the kings justified his rule by claiming to have been saved by the gods when his mother placed him in a basket covered with pitch and set him adrift on the river where he was rescued by the king's daughter. These stories predate the OT by 1000 years. Kings regularly went up onto mountains to receive the law from the local god. There's a picture of it on the Hammurabi stele.
The Egyptian religion was in full flower in 3500BC when history begins and flourished until about 600AD. If you go back beyond 800BC you find Yahweh with a consort named Asherath, burnt offerings, and the occassional human sacrifice so I'm not sure where you would want to count from. At any rate, I think most people would agree that Christ was the founder of the Christian religion. To call Judism "proto-Christianity" is about as insulting to Jews as you could possibly be. That's the equivalent of calling Christianity "proto-New Age" or "proto-Scientology".