He has a condition known in popular liturature as "scissor beak". It will need routine trimming to keep it from getting worse. It is probably a deformity of the ligaments and delicate strucures in the upper beak, and a bird his age is may be the result of trauma.

The harsh chewing of the cage is his effort to correct the problem. He needs professional help with this. I use a dremmel tool with a cone tip to do this procedure, as do most avian vets. If there was some other technique used, or if the vet staff is not used to restraining macaws there may heve been a problem with it. If you did not use an avuian-experienced vet, I would suggest the you find one. Check the link http://www.aav.org/association/index.php?content=activeMembersList for members of AAV in your area or call your regular vet and see who they recommend.

You cvan do physical therapy with the beak, this sometimes improves it over time to the point of minimal trims. "pinch" the beak sideways the opposite direction of how the scissoring goes; this will stretch soft tissues for more flexiblility.

Added calcium is probably not going to help, and anyway additives are only a second choice to diet. Birds should be on a high-quality, preferably prescription, pelleted diet. In addition, they should be offered dark leafy greens, cooked sweet potatoes, yams, squash, pumpkin; entire (tops and bottoms) fresh carrots and so forth. No seeds (and that means a mix, or millet, or sprays, etc etc.) and only healthy, low-fat high fiber people food. A dietary change should be closely monitored and supervised by your avian vet.