I would definitely get him to a vet that specializes in aviary or farm animals. First labs to make sure WBC, RBC and liver enzymes are within normal limits. Based upon those the vet might suggest the biopsy or whatever those labs indicate. Your poor roo looks absolutely miserable. Isolation is a good first step. Terramyacin is a broad spectrum antibiotic but in this case I wouldn't do anything except isolate him until you can get him to a vet. Best of luck to you. So sorry you and your sweet roo are having to go through this. Sending warm wishes, prayers and hugs your way.