Unfortunately, dental abscesses in rabbits (particularly in lower jaw) can often be an ongoing battle. I do think you’re in a better position for success now that problematic teeth have been removed.
I know how dreadful they look after that 1st surgery and can understand your hesitation in doing it again. Do chat with your vet more extensively about it. Sometimes reopening the site is not as big ordeal as the original surgery and if pus is building up, it might even help relieve pressure if that’s an issue.
The vet may be thinking of marsupialization (or re-marsupialization?) to keep the wound open longer remove any pus still being produced and give antibiotic a chance to take care of pathogens causing it. I would discuss doing the wound flushing daily at home if you do go forward. And if you’re not too squeamish and Fluffy is compliant.
The antibiotic beads were not available here in Australia back when I was dealing with dental abscesses (2012). It may have been bicillin specifically that wasn’t available and that was what was recommended at the time.
i hope there are more options now.
I do agree injectable antibiotic like penicillin g might be beneficial.
You could have the pus cultured but chances are the current antibiotic could effect results. Also, often a secondary bacteria shows up in results but it not necessarily their original culprit for the infection.
I had some success treating an excised facial abscess wound in a rabbit with medical honey. It was messy but it seemed to help keep the wound really clean while it closed up.