Every day I wake up and find more reasons why the Usopp dying and coming back to life (like g5 luffy) via "devil" mushroom seems even more likely. Especially since Jango's powers are distinctly not from a devil fruit.
From the way he addressed Garp and Sengoku here, I'm sure that he most definitely knows about Rocks' mission and the truth of God Valley. Especially since it was right after he claimed his 2nd devil fruit and part of Rocks' plan was that he needed 2 devil fruits