I am familiar with the numerous alternate theories, some of which you mentioned. I am also familiar with the theory that Mohammed was a myth created by the Catholic Church. I have seen several websites about that very same subject. Interesting. And I cannot comment on the validity of those arguments because I don't know enough.
However, regarding the "Jesus" myth, I followed the trail of the Biblical elders along the Old Silk Road. I do believe they existed. Myths don't leave graves. I do believe their ties with India and the Himalayas are much more intricate and profound than previously recognized. There are so many "lost" and esoteric texts...the Gospels of Adam and Eve being especially daunting...then there are the theories from Zacharia Sitchen and Von Daniken...
So the project for our minds becomes like choosing foods from a menu. "It's Tuesday so I think I'll try the roast duck..." We each make personal choices in our reading and our beliefs..until there is more science we cannot be sure who is right or what is right, so we make personal choices. And even these change as we read and learn more..It's good to offer up a lot of alternatives...but the truth is, we still don't know with certainty. That's why I asked that at least some of those ancient graves be opened for some kind of verification.Till then, the jury is still out. :-)
© Charles N. Pope, US Library of Congress. All rights reserved.