You probably could lower the temperature to the lower seventies without too much trouble, and that would be desirable.
Most people feed their octopuses either every day or every other day. As Colin says, it is important to feed a variety of things to approximate what the octo eats in the wild - there's a wide choice -shrimp, crabs, mussels, clams, scallops, fish, etc. It seems a good idea to give your octopus some live food that it can hunt, too.
Nancy