Quote 7
The war would be deadly all right. But I was used to finding something deadly in things that attracted me; there was always something deadly lurking in anything I wanted, anything I loved. And if it wasn't there, as for example with Phineas, then I put it there myself (7.115).
This hits an odd note for Gene. Either he's genuinely masochistic (unlikely), or he's desperately trying to justify his earlier actions.
Quote 8
He needed me. I was the least trustworthy person he had ever met. I knew that; he knew or should know that too. I had even told him. I had told him. But there was no mistaking the shield of remoteness in his face and voice. He wanted me around. The war then passed away from me, and dreams of enlistment and escape and a clean start lost their meaning for me (8.45).
Gene may have stopped himself from enlisting, but by staying he's joined another kind of war, a war of his own making, having to do with Finny. (Against Finny, or with Finny? Tell us what you think.)
Quote 9
Phineas recaptured that magic gift for existing primarily in space, one foot conceding briefly to gravity its rights before spinning him off again into the air. It was his wildest demonstration of himself, of himself in the kind of world he loved; it was his choreography of peace (9.63).
Gene's description reflects the way in which he makes himself and Finny into a dichotomy of warlike enmity and peaceful amity.