I bet Oro feels the same way about his parents that Sasuke does about his clan and the village. They both have severe identity crises, fulled by the inability to intervene when they were faced with their individual tragedies. Since then Oro and Sasuke have been both searching for power, maybe for different reasons but similar enough that they are compatible. We saw that sasuke was able to overcome his ignorance that allowed people to take advantage of his tallent many times, and because of that perhaps Oro sees a purpose in helping him now discover the history of his clan and the leaf. Like Oro said, Sasuke has been used by many ppl and was able to defeat them and free himself. Plus after seeing Itachi's love and dedication to the village he must wonder why he acted the way he did, giving up his life and forsaking his clan for the better of the village.
I think also that Oro aside from his behaviour, truely does love the Leaf village. In the manga i always thought he didnt look fullfilled destroying the leaf of fighting those from the leaf, the only thing is his conviction to his goals override his love for the village, He needs to complete his body and learn everything he can about jutsu and nothing will stop him.
And even though Itachi did stop the Edo, I dont think that was the end of his promise to Shisui to protect the village. That being said i dont think sasuke is losing his conviction to crush the leaf, he's realizing that his ignorance is the reason that he was used by so many people and he's trying to fix that by getting information from the source. He knows only Oro can help him accomplish this.
On a side note, i think Orochimaru has already perfected the sage mode, and even if he hasn't done so, he has knowlege now from observing Kabuto fight Sasuke and Itachi. Im excited to see what he can do, i still think Oro is more powerful than the other sanin, not in raw power, but in foresight and strategy.
Look at it this way, Oro doesnt care about the war, he was only gathering data on the sage mode while his consciousness laid dormant in everyone with the cursed seal. All he has to do is reabsorb his chakra from anyone he placed the curse on and he can aquire the data they have. If he enters a fight with the knowlege he has now he'll be on par with any of the top teir shinobi, and he was already a powerhouse.
....i hope he can revive Jiraya lol
