the gemarah says that hashem listened to those of earlier generations. at first they thought because they knew more gamarah(13) so what the gemarah said whether one learns a lot or a little as long as he does it for hashem?
also y does rav huna say one can say kedusha by himself? does he argue on v'nikdashti? also y does rashi say b'zibur'?
(a) True, the important thing is that one be sincere and have genuinely pure intentions in his Torah study. But still, Rav Papa -- whose initial suggestion was that the earlier generations were greater because they learned more -- assumed that there nevertheless is an advantage in knowing more Torah, at least with regard to deserving that miracles be done on one's behalf.
Furthermore, the conclusion of the Gemara is that even though they did not know more Torah, nevertheless they were still greater! This itself is a proof to the Gemara earlier that it does not matter how much one learns, but what matters is that his intentions are pure and sincere!
(b) Rav Huna does not say that one may recite Kedushah when Davening alone with no one else around. He says that an individual may recite Kedushah when he is in a synagogue in which there is a Minyan. Since the Shechinah is there (because there are ten men), Rav Huna does not require the ten people to recite Kedushah together. As long as there are ten men there, a person may recite Kedushah by himself (this is what "v'Nikdashti" teaches).