“A big problem with that pshat is that the quatity of oil for his mincha was considerably less than would be required to light for even one day.”
The following comes from the sefer Hegyonai Halacha by R’ Mirsky (my translation and paraphrase):
The Chavitin required 3 log, whereas the Menorah required 3.5 log (1/2 log per ner times 7). There is a different girsa of the the shiltot of Rav Achi Goan. Our Gemaras say that there was not enough oil except for one day (eleh l’yom echad), but his girsa says that there was not enough even for one day (afilu l’yom echad). Another answer to the question of the Beit Yosef.
Another problem is that the oil for the Chavitin is of lower quality. The K”G, however, used the highest quality oil, even good enough for the Menorah. That is why Hanukkah has Mehadrin and Mehadrin min haMehadrin, unlike any other holiday. They were so careful about all their Avodah and so we also inherit such hiddur.