Whites are the actual Jews

A person of Middle Eastern heritage will have a shared ancestry with various ideological adherents.

Though selective breeding will no doubt refine DNA.

And with others of similar geographical origin if you go back far enough. Intermarriage between groups and fluid group memberships will make DNA a useful but not exhaustively thorough resource.

Yes, and one can find plenty of studies that try to show lineage and group affiliation in Judaism as attested by DNA; you can find studies that cite evidence to prove the opposite. Both , of course, ignore conversion and rape, but the studies exist.

How is it not "grounded on earth"?

Do you have a link to a full pdf?

Thank you.

Because it is fantastical.

I still don't grasp your meaning when you state it's "not grounded on earth" or "fantastical." I can understand--like oromagi suggested--that new studies cast doubt on Koestler's findings, but that doesn't suggest that his findings are without merit, or at least without merit during the time his research was conducted. Furthermore, most if not all the references you listed, with exception to the jstor link, spend too much time appealing to Koestler's motives and the allegedly nefarious intentions of those who employ the Khazarian theory. Admittedly, I'm going to have to do more research into the methodology of these new studies, given that what I've  read thus far has made no explicit mention of sufficient controls.

Whites are the actual Jews 

Ashkenazic Jews are the Jews of France, Germany, and Eastern Europe and their descendants. The adjective "Ashkenazic" and corresponding nouns, Ashkenazi (singular) and Ashkenazim (plural) are derived from the Hebrew word "Ashkenaz," which is used to refer to Germany. Most American Jews today are Ashkenazim, descended from Jews who emigrated from Germany and Eastern Europe from the mid 1800s to the early 1900s. The pages in this site are written from the Ashkenazic Jewish perspective.

Today Ashkenazim constitute more than 80 percent of all the Jews in the world, vastly outnumbering Sephardic Jews. In the early 21st century, Ashkenazic Jews numbered about 11 million. In Israel the numbers of Ashkenazim and Sephardim are roughly equal, and the chief rabbinate has both an Ashkenazic and a Sephardic chief rabbi on equal footing. All Reform and Conservative Jewish congregations belong to the Ashkenazic tradition.

So the majority of Jews today are descendants of European women converting to Judaism.