Jack was curled in on himself, panting hard, by the time Ennis pulled back. Somehow, he managed to keep conscious, even if he desperately wanted to pass out, to stop the pain.
Still, if there was ever a reaffirmation he was alive, it would be the intense pain he was feeling. And it was better Ennis took it out on him, than on himself. It was him damn fault, after all.
Jack didn't approach Ennis, or even move, afraid that wouldn't be the end, if he did. He just lie still, essentially playing dead until things were calm again; if they ever would be.