the only exception for not going kyuubi in part 2 would be kakuzu.But other than that he went kyuubi on all of the other major enemies.
We proved that he did use the Kyuubi on Kakuzu, though he was in 0 tails.
I still am not convinced that he used Kyuubi to defeat Kakuzu.
Note: I am not saying you are wrong, but I'm not saying you are correct either.
Leading up to that moment, they had focused on how Naruto had to
NOT use Kyuubi in his future development/fights.
In the Manga, I saw the panel you referenced, and I understand completely why what you say makes sense. However, neither Yamato nor Kakashi (nor anyone else for that matter) mentioned that he had "slipped" or in any other way indicated that he had reverted to using Kyuubi.
Again, I'm not saying he didn't, but I am not convinced he
did. One panel is not going to seal the deal for me.