After following this for a few days you get so emotionally invested. Poor trousers, so many people are pulling for him. I'm an anesthesia specialist, not exotics but cats and dogs, and i don't believe this is a reaction to anesthesia. I just tried going back a few pages to check but he was doing better right after surgery and didn't start having trouble until the next day correct? A reaction to anesthesia would be immediate. Pets who have reactions tend to wake up from surgery displaying neurologic symptoms. I was about to post the other day that i felt this was a embolism issue and that he'd thrown a clot. Symptoms such as paralysis and weakness will appear out of no where. Did you ask your vet about the pain meds? I know you are nervous to give them nut i really don't think they are the cause. It is also normal for his stool to smell weird because of the meds given during surgery such as antibiotics. They also probably smell different because his diet is different than normal.
I know this doesn't help you but hopefully mine and all of the members positive vibes coming your way will.