1. Naruto does have Senju blood in him, the Uzumakis are relatives with the Senjus.
2. Itachi's "undead" state will most likely end, as the user of edo tensei can end by the summoner. However, this can relate to the control of the technique, not the mind-bind-to-body. If this isn't the case, I don't see why not Itachi would not confront his brother.
3. The reason of activating Shisui's eye, the techinique is by far on a high level genjutsu and requires a decade to reactivate. This is based on chakra and stamina. The reason why Harishima could activate it once more, is that the Senjus have monstrous stamina and can withstand the jutsu. Ex. Kakashi cannot use the Sharigan effectively because he does not have the stamina of a Uchiha.
4. Just because Itachi's gift happen to work, does not make him a super Shinobi. That gift was meant for Sasuke, but it happened to activate on him.
5. Nagato sucked up Bee's chakra, and is currently sucking up Naruto's soul.
6. Having "Wood" element is no different than having crystal element, or dust. It just so happened that he had the element that relates to all things in life. All Senju have incredible Stamina, not just Hashirama, but it was his wood element that made him hokage.
7. Getting DNA from Yamato would not help, they would have to experiment with Naruto then, plus Naruto already has Senju blood. Very much like Danzo, not being a direct and/or descendant of a Senju, does not have the Stamina, and so his chakra was drained quickly.
Side note:
8. Madara Uchiha has Hashirama's DNA within himself or is using a body that has one. How else do you think that he is able to go into trees and objects, but not water? It's most likely the coffin is not Madara's, but I would guess Madara is able to live for so long is because of Hashirama's DNA. It would be more surprising if the coffin was the Sage of the Sixth Paths.
Just to clear some stuff up.