My initial thought is if your rabbit vet advises against spaying due to anesthesia effects on a small rabbit, finding a vet who is more comfortable doing so is important — if experienced enough, a rabbit vet will not have issues spaying/neutering a small rabbit. Some vets, based on their experience, may not be comfortable with that, and it’s important to respect that, while also considering what this means about their success rates versus someone who is comfortable with it. This doesn’t necessarily mean your specific vet is not experienced enough with rabbits, but perhaps in the realm of doing spays/neuters, there may be someone more qualified and confident, which would translate to potentially better results.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.