1. What are the differences between his "Budo", "The Essence of Aikido" and "The Secret Teachings of Aikido". And where could I find some of O sensei's meditations, breathings and philosophy.
All three are great books. Budo is a kind of manual put together by students of M. Ueshiba with his permission and given to select few students as a kind of thank you. It was written before the war. The english version was translated by John Stevens. The Essence of Aikido was compliled by John Stevens and contains translations of talks and poetry by the founder and includes a lot of photos of him in action as well as his calligraphy. I have not read "Teachings" yet, but believe it is another translation, maybe someone else will comment on it.
Personally, I recommend John Stevens' "The Secrets of Aikido." In it, Prof. Stevens lays out the spiritual teachings and ideas of M. Ueshiba and explains them using examples of other cultures and people both in and out of Japan. As for breathing and the like, I also highly recommend John Stevens' dvd called "Misogi." The stuff is much more easy to learn visually. Of course, if you could attend a seminar that would be great, Prof. Stevens is very approachable.