What iss jack obsessed with? Why does he want to do this? What does he neglect?

You have a few questions here. Jack is obsessed with hunting. If we consider the subtext, he is actually more obsessed with killing. He feels compelled to cut into flesh and take life. Jack is able to validate his thirst for killing under the guise of getting meat for the boys. Jack neglects responsible activities that he promised to do. He does not help with shelters and is not serious about keeping a signal fire going.