It says the book had the power to do that, not that it actually did it.I think that the sentence as written implies that Nyudo did, in fact, attain Buddhahood, whereas "toward attaining" would imply that he made progress toward Buddhahood but did not attain it. Others may disagree.
I would say that you can lead someone to Buddhism, but not to Buddhahood. You can lead a horse to water, but you can't make it drink.I would omit the verb: "... the true teaching that had the power to lead her father, Matsuno Rokuro Zaemon Nyudo, to
You can lead someone to a place where they can be happy, but that won't make them ecstatically happy. I think you can lead someone to (join a) religion, but that doesn't cause them to become the Pope (to switch religions).Hmmm... I don't know about these things but "It was the marriage to the millionaire Sir Myridon that
leadled her to happiness.": to lead someone to a state seems OK.