Okay, it sounds like you're doing a lot to help. The neosporin was a good idea. If part of her foot is dead, it may lead to necrosis and death, but I don't have a picture so it's not certain. (I am also not a vet, take this with a grain of salt.)
I'd be cautious using the coral. Some of it might be sharp. I wouldn't put it in water because salt might leach out. Toads aren't normally big climbers anyway.
I'd continue applying neosporin occasionally and let the toad alone to rest in between. Sorry, I don't know how to amputate a foot or if this would be feasible or a good thing to do. hopefully someone else can answer.