In addition to NOT feeding the dragon ANY solid foods, please remove all of the Eco Sand from the dragon's tank, they do not naturally live on sand, the Australian Desert is a hard, rocky terrain with little sand, and you need to use only a SOLID substrate that is easy to clean, and that he cannot lick and ingest, as they lick everything constantly. Especially a small baby, even a very small amount of calcium sand, regular sand, crushed walnut shells, wood chips, bark, rodent bedding, etc. can kill him quickly, and this is very likely part of the problem, in addition to any damage the cat did. The other issue with ANY type of loose substrate, and sometimes a bigger issue than impaction, especially when they get older, is that Bearded Dragons are very prone to bacterial and fungal infections of their Respiratory Systems, their eyes, and their skin/scales, and ALL loose substrates are breeding grounds for all types of bacteria, fungi, parasites, etc. as soon as you put fresh in. Respiratory Infections are very, very common in Dragons on loose substrates, as well as serious, fatal fungal infections like Yellow Fungus, which grows internally as well as externally, and is extremely difficult and expensive to even attempt to cure. So please, dump out all of the sand and then completely disinfect the entire tank, including all of the decor and bowls in the tank with very Hot Water and either Bleach, Hibiclens, or white/red wine vinegar, and then just put down clean, dry paper towels and replace them as they get dirty. You can then worry about choosing an appropriate solid substrate that is permanent, like textured tiles, non-adhesive shelf liner, reptile carpet, etc. Please, do not hesitate to do this, as he cannot take ingesting anymore sand right now, it clumps and hardens when it gets wet, and he cannot handle it anymore.
As far as the kitten goes, the dragon must always be kept in a room with a latching door that is always off-limits to any and all kittens/cats, they can never be allowed to be in the same room, as kittens/cats are natural hunters, it's an innate trait that all cats have, and it's not their fault, but they will never stop trying to get at the Dragon. Even allowing the cat to just sit near the Dragon's tank and stare at him will cause extreme stress for him, as he knows there is a predator right outside his tank. They somehow manage to knock lids off of tanks, reach in and pull dragons out so they can torture them to death, knock entire tanks over, etc. So that's why I always suggest choosing a room that has a door that latches and that the cat cannot open, that everyone in the household knows is completely off-limits to the cat. That's really the only way to keep any and all small reptiles safe and stress-free when living in the same house as a kitten/cat.
As far as injuries sustained, Tracie and Knobbys already said it best, you have absolutely no idea if the poor little guy has any internal injuries or bleeding, as all kittens and cats love to "bat around" the prey that they hunt, that's usually how they end-up killing mice, birds, bunnies, etc., they basically torture them for hours until they bleed to death internally. And it's very likely that the kitten took a swipe or two with his claw at the dragon, he could very likely have a puncture wound somewhere, or more commonly internal injuries that only an experienced reptile vet can do imaging studies to find and possibly treat. So getting him to an experienced reptile vet is really the only thing you can do, as there are no home remedies for internal bleeding. He very likely is in "shock" just from the attack, the best thing you can do for that is offer him fluids dropped on his snout several times a day for him to lick off, maybe bump up his tank temps 5-10 degrees, and just keep him quiet and warm, but really only a reptile vet is going to be able to help him if he sustained any internal injuries from the kitten.
