This is such a tough situation - it is like the incurables program and humans. Plus - there are certain foods that Rabbits are never supposed to eat, ie onions. I don't think we've had an expert vet on the site.
But if you are close to putting the animal to sleep - I personally would try hot cold hydrotherapy on the area, would go to www.herbsfirst.com and order garlic/mullein oil and ear nerve tincture. I would even make some garlic oil (with olive oil) as the shipping time is going to be prohibitive in the meantime and get that in the ear. Dr. Christopher's approach is to put the garlic mullein drops, 2-3, in, then add 5 - 10 drops of the ear nerve tincture, closing the ear with cotton. One could also massage the tinctures on the spine and outside the ear.
As I do not know the interaction potential with a Rabbit - the caveat is that I would try and find a qualified alternative vet. But in dire straights - I would try it on my own if the alternative was that the animal was going to pass anyway.