1)
Why did they kill many people?
1.
Malbim: Many wanted to make Shalom with Nebuchadnetzar. They fought against them, and killed them.
2)
Is increasing dead bodies connected to the previous verse?
1.
Rashi: Yes - you plan to remain in the city until death. The dead bodies that you put in it, they will remain, but I will remove you from it.
3)
Where is "Chutzoseha"?
1.
Malbim: It is in back of the houses. People do not see there like they see in the city. They filled them with bodies, for they killed covertly.