This is now 24 nights that Skye is sleeping outside but we are making some progress... And we are starting to catch up on sleep or at least stop losing it :)
5 days ago, we shrunk quite drastically the yard at night (see latest fencing setup) and it really helped decrease Skye's nocturnal arousal. She didn't bark as much. Actually she was able to sleep at least 5 hours in a row 4 out of the 5 nights. And in the early morning (3-5am), I was able to get her inside the house to finish the night (where I ended up on the sofa to keep her company).
I wish she would come in the house by herself in the evenings, as I am really wary of closing the backdoor at night. I really don't want to go through another setback (and sleepless period)!