Actually, the height of "Jewish" participation in the USSR was during Lenin's reign. Stalin actually purged most of the Jewish leadership in the Soviet Union and, despite being a Georgian, made the leadership more Slavic. Nevertheless, I see your point.
Yes, that's true, but that came later after they served his purpose. Lets also not forget that there are 2 different kinds of Jews were are talking about. Those evil ones still have control in Russia's elite dark underside. They aren't really "Jews" at all. They are true communists.
Stalin made alliance with Hitler. They were really very much alike. They were both anti-Jewish Socialists.
Sometimes I think that the main reason Hitler hated the Jews was because Hitler WAS a committed Socialist, and he ran into German Communists who didn't want to let Gentiles into Communist leadership positions