Jack's hands were a little less steady on Ennis' belt, as he wasn't exaggerating his exhaustion, still, he was bound and determined to work through it, at least until the two of them found relief, became balanced again.
After a minute of fumbling, he managed to get through all the fixtures, and get his hands against the skin of Ennis' hips, moaning when he did. He knew it would probably be the last act he had a say in, until things were over, so he wanted to enjoy it.