I would also recommend finding a more rabbit-savvy vet. It seems a little odd to me that they wouldn't be able more fully diagnose the extent of the injury... the visual exam should be able to provide more information, regardless of whether the rabbit is showing signs of pain. Did the vet use a fluorescein dye test to evaluate the abrasion? You might check to see if there's a veterinary opthamologist nearby who specializes in pet eye issues.
My bunny had both an eye injury (possibly cat-related) and cataract formation due to E. cuniculi infection. My vets are quite thorough, but they referred us to the veterinary opthamologist for a second opinion, and both vets worked in coordination to diagnose and treat my bunny. We treated the eye injury with flurbiprofin drops and gentocin ointment (an antibiotic), and later treated the E. cuniculi with fenbendazole--aka Panacur, and we were able to save the eye. However, there was the very real possibility that he might need to have his eye removed, and my vets and several websites assured me that rabbits actually manage really well with one eye and can have a high quality of life after the problematic eye is removed. So that was reassuring!
It sounds like treating the infection and pain are both really critical right now, but if they're recommending eye removal, it's likely because the infection has gotten too bad and the damage is too severe (although it would be worth getting that second opinion!). The sooner you can have it removed, the better his chances will be of recovering. Infections aside, when bunnies are in pain, they often stop eating, and... that's bad news
Sending healthy-eye vibes to poor little Meatball!!