I don't know what you are feeding, but perhaps a little higher protein and less grain may make him feel a little better. If the foot is hurting, it may be what is making him sluggish. If he is licking, it hurts. Have you tried water therapy on it? Also, wearing a sock makes some of mine not "able" to walk
Did they tell you to give pepcid, tagamet or zantac with the clavamox? Some greys have tummy upsets with it after several days.
I have a feeling the contact and working with Ohio State will be effective :)
Sending lots of prayers. It sounds quite frustrating.
Has he had a TBD panel done? Thyroid?