Quote 4
I threw my hip against his, catching him by surprise, and he was instantly down, definitely pleased. This was why he liked me so much. When I jumped on top of him, my knees on his chest, he couldn't ask for anything better. We struggled in some equality for a while, and then when we were sure we were too late for dinner, we broke off (1.46).
Gene will later remark that few scenarios at Devon are not governed by rivalry. This, then, is how he conceives of his friendship with Finny. Wrestling together is a reflection of this healthy sense of competition, on which, as far as Gene knows, their friendship is based. This is why he feels so confused later, when he realizes Finny isn't concerned with competition between them.
Quote 5
What was I doing up here anyway? Why did I let Finny talk me into stupid things like this? Was he getting some kind of hold over me? (1.32).
The notion of equality is important to Gene when he considers his friendship with Finny. Much of his hesitation over jumping has less to do with a fear of dying than a fear of subordination, of blindly following Finny's desires.
Quote 6
The point was, the grace of it was, that it had nothing to do with sports. For I wanted no more of sports. They were barred from me, as though when Dr. Stanpole said, "Sports are finished" he had been speaking of me. I didn't trust myself in them, and I didn't trust anyone else. It was as though football players were really bent on crushing the life out of each other, as though boxers were in combat to the death, as though even a tennis ball might turn into a bullet (6.93).
What Gene has done by (allegedly) causing Finny's accident is to break the barrier between the war and the innocence of youth. That's why sports are over – there's no such thing anymore, in Gene's mind, as harmless play. Compare this passage to Finny's conception of sports (in which they are purely good and no one ever loses).