What I did notice, however, is when Jack woke up and grabbed Ennis' hand, the tent was tied closed..When Ennis first came in the tent, it was open and both guys went right to sleep.
You are correct deedee. When Ennis was outside freezing and Jack was in the tent, the tent was tied. Jack untied it to tell Ennis to get inside.
Ennis enters the tent and goes to sleep, the tent is still untied.
Jack grabs Ennis's hand, they get up on their knees and the tent is somehow tied again.
They have sex, fall asleep again, the tent is tied.
Ennis wakes up and the tent is once again somehow untied.
Someone here will probably say that Jack wasn't very drunk so he got up in the middle of the night and untied the tent to let cold air in to sober Ennis up.