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You're speaking to Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply.
I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. As you might imagine, assessing musculoskeletal disorders/trauma from a distance is quite difficult for me. I would examine Salty's leg from the tip of his toenails to his hip looking for subtle changes in his foot suggestive of pododermatitis (bumblefoot) or articular gout (seen in association with chronic renal insufficiency) in any of the joints of his leg, as well as swellings or other skin changes suggestive of sprains, strains, or neoplasia (cancer). Hypocalcemia (low serum calcium level) might result in lameness as well. I don't believe that his beak behavior is related to his lameness but your idea is certainly valid.
I expect that his avian vet will perform such an examination and if nothing untoward is found, recommend X-rays and diagnostics in the form of blood, urine, and feces testing. Please respond with further questions or concerns if you wish.