In any case, you've made some good progress - I'd encourage you to keep up with the soaks and packing antibiotic ointment in there to fight the bacteria until it is all finally resolved.
I do read about the "seed" or "kernel" needing to come out. Is it possible this bumblefoot is some kind of fungus? In that case, something like oil of oregano or tea tree oil might be useful.
I wish there were a picture encyclopedia of foot problems and their resolution, not just one or two examples but a variety of cases from mild to severe, with appropriate treatment that can be done by mere mortals. I picked up a book of poultry diseases and found just a few pictures of extreme cases of bumblefoot on chickens' feet.