"But he says Jews. Why? Because "it was the Jews who started the slave revolt in morals". Because they are prior, seminal. But let's not confuse description with prescription. Of course, Nietzsche is offering a genealogy, which was really a great innovation, a powerful tool for philosophy."
We can cut down your long statement and get to its kernel, all this talk about 'genealogy' simply means he is stating the following: the Jews started the catastrophic moral revolution which has led to our current miserable situation, of decadence, etc.
You can hand wave about how it's not anti-Semitic because all he is saying is the Jews 'just happened' to come first and he gives us a powerful new tool, but the point is there for all to see. Human civilization used to be growing, vital, creative, and life-affirming. The Jews more than other group, he says, is responsible for reversing all of this. He even goes as to far as to say the following:
"Rome viewed Israel as a monstrosity; the Romans regarded the Jews as convicted of hatred against the whole of mankind -- and rightly so if one is justified in associating the welfare of the human species with absolute supremacy of aristocratic values."
The Christians are lumped in because after all, they spread this Judaized morality, being a sect that is derived from Judaism.
Now, I suppose one can say that it's not anti-Semitic to declare the Jews responsible for all the world's ills hated all of mankind, that it's just honest reporting of the facts. But I think it's rather plain that Nietzsche cannot be absolved from responsibility for the Nazis using these words to mean that the Jews are a scourge on society and weaken every country where they come to be of influence. And since Nietzsche elsewhere rather gleefully expresses approval of "life-affirming" actions, like domination and violence, Nietzsche also provides a method for how to solve the problem.
From the Genealogy of Morals
"No act of violence, rape, exploitation, destruction, is intrinsically "unjust," since life itself is violent, rapacious, exploitative, and destructive and cannot be conceived otherwise. Even more disturbingly, we have to admit that from the biological point of view legal conditions are necessarily exceptional conditions, since they limit the radical life-will bent on power and must finally subserve, as means, life's collective purpose, which is to create greater power constellations. To accept any legal system as sovereign and universal -- to accept it, not merely as an instrument in the struggle of power complexes, but as a weapon against struggle (in the sense of Dühring's communist cliché that every will must regard every other will as its equal) -- is an anti-vital principle which can only bring about man's utter demoralization and, indirectly, a reign of nothingness."
"No, neither, he was referring to the aristocracy that applied its values, prior to the inversion, for after the inversion there was no going back, and what was the aristocracy too was forever changed. That aristocracy no longer existed and under no circumstance was it embodied or re-incarnated by the nazis. The values had been reversed, the Nazis made the mistake of thinking that the reversal could be undone,"
Where does Nietzsche say that this moral inversion cannot be undone? He didn't say it in this passage, and I haven't read anywhere where he says it. But if you can point this out to me it would do much to convince me that I am simply misinterpreting a man who just likes to write in an exaggerated and convoluted style.
In his genealogical account of "Rome vs Israel, the classical ideal vs vindictive popular instincts", he seems to indicate that Jewish moral supremacy has been anything but settled. It dominated from the Fall of Rome until the Renaissance, where the classical ideal reappeared. Then it fell again with the Protestant Reformation and the French Revolution, only to reappear again in the person of Napoleon.
Read here for his talk of the Battle of Rome vs Israel
http://teachers.sduhsd.net/gstimson/genealog.htm
Hitler could have easily interpreted this to mean that it was possible to restore the classical ideal and defeat what Nietzsche calls "Israel", and the world needed a Roman inspired militarist to do it.