We recently adopted out a dog at the shelter where I volunteer who had been returned 5 times!! This last time the adopter let us know how it was going. He said the first night was rough. He and Chaco (a Boston Terrier mix) went to bed and when his wife came to bed Chaco peed on her!
And now Chaco is closer to the wife than he is the husband.

Just give it time. It sounds like you are doing all the right things. What happens if you are not home for the night? Maybe start trying that out now before you move away to college.