No third person.
That's fine. I never did like tanks for Beardeds. That don't hold heat well. White Melamine cages work very well for Dragons. They hold heat and they're very bright. 78 is fine on the cool side.
If your Dragons eyes start sinking in, there is a good chance you have a Coccidia problem. It could be other things, but this is the most common. Just keep an eye on it. A Dragon that's brumating still looks very healthy, it's just not that active. It can be hard for the newbie to figure out if their Dragon is sick, or just brumating. If you still have an issue with it's feeding, you're gonna need to decide if you think it's sick or not. If you post pics, we may notice something you don't.