Who is in control of nature/everything?

Okay, so it has been a long time since I read The Battle of the Labyrinth so I might have got a few things wrong, but throughout the rest of the series and into the Герои of Olympus the part where Pan dies has presented a Вопрос which has been bugging me the whole time.

Pan is the god of nature, right? And everything is part of nature; me typing this now is affecting nature, because I'm breathing out carbon dioxide, the computer is releasing heat into the atmosphere etc. Nature includes both life and death and everything. Does that mean Pan was the god of everything? And when he died, he passed his nature powers to Grover...does this mean Grover is now the new nature/everything god? Doesn't this mean he is now the most powerful being alive???
And another thing; Kronos originally used to be the god/titan of the sky, but was replaced by Zeus. If Percy and the other Герои defeat Gaia and condemn her to Tartarus или whatever they plan to do to her, who controls the world? Does Grover control it, if he is now the god of everything??? I'd be very grateful for any answers, this Вопрос has been bugging me for ages...