I agree that he kept on in the war following Tomoe's death because he had given his word. Wonderful, stubborn, pigheaded Kenshin

The fight with Jin-e is more problematic, because he *almost* loses it there, but he is able to keep control in the end. Barely. On the other hand, he's had 10 years for the horrible, mind-numbing death of Tome to work itself into every part of his soul. Right after her death, he was still a very young man, very committed to his cause, and wanting to set things right in the world.
The other question, though. Wow, that's a good one.
If I remember correctly, the final secret was only effective when its student realized that he HAD to stay alive because there were things to do that only he could do. (Incendentally, this is the same "life IS worth living and I have things I must not lose" message that moved me so much in Slayers. Howzzat for a contrast). Now... if he was able to master Hiko's final lesson would he be even more convinced that his sword should be used to bring about the new age? To protect the people who were suffering? Or would he have become a pacifist?
I'm leaning toward the idea that he would have still participated in the war, but more openly. I'm thinking he would not have agreed to be an assassin. But I'm not sure why I'm leaning that way. Maybe because the additional power and the confidence it would bring with it might have fed into that little streak of arrogance that sneaks out every so often... and he wouldn't have felt the need to work in the shadows.
But maybe that's way off.
Hmm! After my tests are over, I must treat myself to a complete re-watch!

(ok, and Kittens... isn't he technically the inheritor of the title Hiko Seijuro anyway, even though he refused to "assume the mantle", so to speak?)
