The second part of the question is the easiest to answer. You shouldn't expect any compensation for arriving late. DL's CoC covers mechanical delays, weather delays, etc. If you were connecting in ATL to somewhere else, their responsibility is to get you on the next flight possible but they have no obligation to get you to ATL by a certain time of day. I and many others on this board have dealt with this situation plenty over the years and I will tell you, I've been stuck overnight and lost nights on paid hotel reservations and everything else and have never been compensated by DL more than what they are required, i.e. hotel for the night in city where stuck, meal vouchers, and frequently some sky pesos for the inconvenience.