Sounds like you got a good one. No barking is a really good thing. What food do you feed, is it the same stuff the shelter used? I wouldn't worry to much if he is over weight. Go lite on the treats, cut them into very small bites and use for training purposes only. If dogs aren't being entertained they sleep that is normal. Don't be worried about him not pooping yet just make sure to take a couple of nice long walks to give him plenty of time to go. Thank you for rescuing. Double thanks because he is 6.