Was the hunching and loose stools (is it actually diarrhea, and if so, did you let the vet know?) occurring before or after starting the Chloramphenicol? If it started to occur after, it could be the antibiotic is causing issues, in which case discussing with your vet about trying a different antibiotic may be worthwhile. If stomach issues from the antibiotic are making him uncomfortable which is causing him to be defensive and reject food, continuing the antibiotic, in my opinion, isn’t worth it, as usually a URI antibiotic course needs to be at least two weeks long.

It is not uncommon for a rabbit to be on an antibiotic for a URI and nothing happen. Many types of bacteria can cause a URI, and different antibiotics will affect different bacteria. For example, Bactrim was first prescribed for Wick, but it did nothing, while Baytril actually did something. Baytril didn’t get rid of all symptoms, so we added Flocillin injections and that did the trick.

I have no experience with Chloramphenicol.

It is concerning that he isn’t walking properly, and you are hearing difficulty breathing. Did your vet listen to his lungs for congestion, and have you called the vet to update on some of these concerns? The aggression towards not taking medication is pretty natural, but not walking correctly and general discomfort doesnt match Wick’s symptoms from his URI. He generally functioned the same, except he’d sneeze constantly. It sounds like this URI has progressed to build up beyond the nose, which could be bad.

The damp cloth is a fine approach to cleaning. If you can follow that up with a dry cloth, that’d help to lessen grooming on your rabbit’s end. Since it is bacterial, make sure not to reuse the same towel unless you wash it.

… This may be a separate topic, but is your rabbit neutered, is the other rabbit fixed, and how long have they been together? It’s possible the aggression has nothing to do with the URI, but has to do with improper rabbit bonding (which starts with both rabbits being fixed). Regardless, it’s good you recognized the aggression and have separated them.