You want consistent water temps. If you can keep you tank about the same temp all year long, I think chillers are not necessary. If you are like me and live in the desert where its gonna be 120 this weekend, a chiller is better than running the AC all day.
Very few fish need water lower than 78 degrees. There are some cold water fish though (Catalina gobies come to mind) and they likely would need a chiller.
So if it got to 95 would that kill most salt water aquarium fish?
None of the ones you will get on live rock will grow any larger than you see there, and they are good scavengers. the ones that eat fish are the ones you see at the LFS for sale. The large green ones.
As for the food, you should have made them feed it in front of you before buying it. They do tend to tell stories here and there. That said, go to the LFS and pick up some live black worms or blood worms if he's not eating. Mine ate only those for a couple weeks, but never went to flake. I've had him a year and he still turns his nose up to flake and pellets. I feed him frozen chopped fish and shrimp mostly, along with nori on a clip of course.