After putting madeline in the vault, usher’s madness begins to increase. why does he get so much worse?

Usher's madness begins to increase because even though he knows his sister is dead, he can hear the sounds of knocking and scratching coming from her coffin. She is dead, but came back to life to haunt him, and thus his madness grows stronger due to his fear of her and death. 

Because writing on paper is said to engrave what your writing down into your brain therefore writing your thoughts is better than speaking them.

As the boys sleep, military airplanes battle fiercely above the island. none of the boys sees the explosions and flashes in the clouds because the twins sam and eric, who were supposed to watch the signal fire, have fallen asleep. during the battle, a parachutist drifts down from the sky onto the island, dead.