No dispute about that, antisemitism as a term to describe persecution of Jews certainly is used to apply to instances that took place 1000s of years ago. That does not mean that antisemitism didn't change, with different forms emerging with different excuses. Hatred of a group of people often precedes rationales for that hatred, excuses are made after the fact.
That doesn't change the fact that hatred towards Jews as a race, hatred towards them on the basis of their birth, their intrinsic nature, as opposed to on the basis of their religion or as a culture, emerged in the 19th century. In almost all of the instances you mention prior to the 19th century, with the exception of the Cossack uprising, conversion from Judaism to Christianity would have spared you. The Cossack uprising and in particular the Khmelnytsky Uprising was not on racial grounds, it was on mercantile grounds and opposed to Jews on the basis of their status as tax collectors as well as propaganda about their collaboration with Polish nobility. Certain Jewish communities seen to have not been involved in either aspect were spared, indicating that the hatred towards Jews was not based on race.
In Nazi Germany, if you were considered a Jew by race, nothing you did could have spared you. Nothing.