Well, as far as AntiSemitism is concerned a Jew remains a Jew no matter what Church he attends. Speaking of the Nazis, again. Jews that converted to Catholicism or any religion as diametrically opposite Judaism as possible even eight, nine generations couldn’t save themselves as non-Jews. The Nazis required ten generations on both sides with baptismal records for every generation to be considered Aryan. Anyone with a Jew in one generation or another were no less diluted from Judaism than some Hasidic Jew. They both perished equally as Jews.
That’s true. The Nazis didn’t care about conversion, but even the Spanish Inquisition required at least 4 generations to be shed being a “New Christian” and it’s restrictions.
Those with mixed Jewish and non-Jewish blood were considered Mischling. If you had one Jewish grandparent, you were considered 1/3 Jewish. If you had 2 Jewish grandparents, you were considered 2/3 Jewish. 3 or 4 Jewish grandparents would classify you as fully Jewish.
A 1/3 could marry a 2/3 but would downgrade in status. To marry an Aryan, you only had to prove 3 generations of non-Jewish blood. You are just flat wrong on your '10 generations' rule.
To learn more, you can start with a brief summary at the Jewish Virtual Library, here: https://www.jewishvirtuallibrary.org/jsource/Holocaust/nurlaws.html