✖ If Nyx can't be stripped of his powers how can he be stopped?
Unless he can reconcile with his mother and brothers, he'll have to be killed.
✖ What is power is Nyx actually the manifestation of?
I'm going to tie this in with another question.
✖ Will Gino be able to inspire the people of Gaia to rise up and resist Nyx?
If he can't, his money will.
✖ Who's going to be recruiting people for the battle to stop Nyx: Edmund, Leon, or Gino himself and will you be willing to fight?
They all will. Sen and Marius too, maybe even Nico and Cres.
✖ What powers could the other three sons be the manifestation of?
For everything in nature, you have to have its opposite to balance it. Meili was tasked with creating life, who else should have the power to take it away but one of his brothers? I think the son who wont intervene for lesser beings is probably in charge of death/the afterlife, so he wouldn't value humanity too much in the first place. The dormant brother may have been in charge of creating land and sea, and now that he isn't needed, he is off sleeping or something. The fourth brother, who is "reclusive", may be the god of natural disasters, whose job it is to destroy brother #3's creation. He hides himself because he doesn't want anyone to see an earthquake or tornado coming. Halo has me convinced that Nyx was in charge of the moon, but what would he do there, other than make sure it stayed in orbit? My theory is that much like our moon, Gaia's moon was once a part of her, but it was separated from her when she collided with some huge space object. Although it benefitted her creation, she couldn't make things grow there. Maybe she put Nyx there so that she could connect with the "dead" part of herself, or maybe he was supposed to protect it.
✖ Is Gaia's long dormant son going to be the god we unlocked in the manga Kickstarter?
Maybe, he could create us another continent.
✖ Who is Gino more mad at Gaia or Nyx?
Gino is mad at himself, for not being able to step into his father's shoes. He may have some hard feelings against Gaia and Nyx, but mostly he is just afraid, insecure, and grieving and he's taking it out on everybody.
✖ Will we get to see the letter next week?
I doubt it.
sad
Bonus Question: Since Gino needs humanity's resistance to boost his power does this mean he's going to have to reconcile things with his brothers?
Probably not, unless he needs them to get the vampires on his side.