“i have never heard that the Rov zt”l allowed/did not object to his talmidim taking pulpits without a mechitza”
I have heard that personally from some talmidim. One took such a position had to leave that pulpit because the congregation would not install a mechitzah (and to this day does not have one).
The Rav z’tz’l was not the only Rosh Yeshiva to encourage talmidim to do this. Rabbi Emanuel Feldman took a non-mechitzah shul in Atlanta with the full approval of Ner Israel’s Rav Ruderman z’tz’l. Rabbi Feldman did suceed in converting the congregation to fully halachic services.
“I am not sure if this was his kulah, but his brother R’ Aharon (IIRC) held that a mechitzah has to be only 39?? inches (for it to be technically at the lowest level, kosher)”
That was also The Rav’s kulah, as well as the kulah of Rabbi Yosef Eliyahu Henkin: Ten tefachim is the required height.
“Yet the Rav zt”l gave the first Talmud shiur at Stern College. Who’s derech then is R. Schachter following in his stance?”
Rav Schachter is a gedol in his own right and can disagree with his teacher. But I’m not sure he really objects to women learning talmud as long as there is proper motivation. He does wear techelit, though, which The Rav z’tz’l did not.
‘if YU has to “take credit” for Mordecai Kaplan’
Mordecai Kaplan did not attend YU; he did study briefly at a predecessor institution, the Etz Chaim Day School. He graduated from JTS when it was still Orthodox and also had a personal semichah from Rabbi Yitzchak Yaakov Reines.
“The proper thing is that a Rosh Yeshiva is just that. The ”Rosh” of the Yeshiva, and is the final arbiter. “
YU/RIETS currently has about three dozen Roshei Yeshivot. There is no Jewish institution in the world that has such a abundance of gedolei Torah.