Re: Ueshiba quote
A version of the quote in English appears on p.179 of "Aikido", written by Kisshomaru Ueshiba, but there is no reference to any Japanese source of the quote. This version is slightly different from the one you quoted, so I suspect that you saw it in a different book. "Aikido" is a revised translation of "Aikido" and "Aikido Giho", combined into one book, but I cannot find the quote in either of these (but I must confess I have not looked very closely\see below). Nor is it among the douka in "The Essence of Aikido" and I suspect it is not a douka, but from a lecture. Some of the other aphorisms given in "Aikido" appear in other places, for example, the early volumes written by Saito Morihiro Sensei under the title "Traditional Aikido".
There are two published editions of Morihei Ueshiba's lectures: "Takemusu Aiki", edited by Hideo Takahashi, and "Aiki Shinzui", edited by Kisshomaru Ueshiba. Unfortunately, there are no indices in any of these works and the Founder wrote so many memorable aphorisms, in much the same definite & assertive style, that looking for a particular one is like looking for the proverbial needle...
I think you need the help of someone who is studying the writings of Ueshiba in Japanese for a PhD thesis or something, if there are such people around.
Of course, if I come across something which looks like the Japanese original, I will let you know.