From your description you seem to be a case of chronic osteomyelitis of your leg bone. It is very common for such patients to have persistent discharge from the infected side for some time. It is easy to differentiate dead bones on the X-ray but at times it is very difficult. If it is visible on the X-ray, surgery is easy. If, however, it is not visible on the X-ray, surgery is risky as we may take out more bone than necessary thereby weakening the bone with a subsequent risk of fracture. There is no point in taking antibodies unless you have systemic evidence of sepsis. Usually this manifests as fever.
If the treating doctor is sure about the bone abscess and you are confident
on his competence, I think it is safe to go ahead and get the surgery done.
One word of caution: once there is infection in the bone, no one can assure
you that they can permanently cure the infection. Therefore be aware that
there is always a possibility of recurrence of infection.