As a student of Korindo aikido, I do have a couple of comments on 4, from items which were told to me (not real historical proof):
a. Hirai was a teacher starting his own path already before he moved to Tokyo and took the role of "general manager of the dojo/organization". Further, Hirai moved from this position to the position in the Butokukai. As far as my teacher asked in the "new Butokukai", they claim back then there were no "representatives", definitly not for Ueshiba (I would guess back then he was not considered too important himself).
So what was his actual position inside of the Butokukai organization? The man who was once the head of the Japanese Army military police jujutsu department sure would be much appreciated in such an organization. Not to mention being the Director of General Affairs of the infamous Kobukan "Hell dojo" , which was also visited by many known people of the time, would add quite the "spice" to his resume.