What a terrible ordeal for all of you! Glad he’s eating again. They don’t get PTSD per se, but they do learn to be afraid from strong stimulants that cause a fear reaction. Example would be someone who picks them up in a way that hurts them, so they get afraid when they see a hand coming at them in a certain pose from then on. It imprints negatively in their brain. I would imagine that a siren might cause him to hide from now on, as a possible sense memory reaction. But any animal is going to go on red alert in the presence of fire and smoke. (Remember Bambi when the forest animals fled the fire?) It’s just a self-preservation response. I wouldn’t expect him to be unusually traumatized after this except around smoke or crashing windows.
There still may be some smoke inhalation issue, so it would probably be wise to get him checked by the vet even though he is eating again. Bunnies do react from stress, so one day off his feed is quite normal.
The clean up for you must be horrible, btw. So sorry and don’t underestimate that you can use some help there, too. I am concerned that any flying glass may have gotten in his living space, so I think (unfortunately) a really thorough clean up of all of his space, dishes, bedding, toys, litter stuff might be a good idea.