Yes they sound very familiar to me. I just had a bout of the heaviness in the chest this past week. If you touch the breast bone it hurts. To take a deep breath hurts.
Also the pain in the muscles can be referred pain. Were the pain in really in the joint or ligaments and is causing the muscles to hurt. I have this in my left shoulder. It can cause pain down my arm to almost my elbow. Below is a link to help with more information. Please feel free to ask any question you might have. We have a wealth of information on this board and willing to share it.
Sorry to hear you son has this awful disease. The good new (if you can call it that ) Is that now you know what it is you can treat it and hopefully prevent any damage to his spine and other joints. I wish I had known when I first had symptoms.
Maybe then I could have stopped my neck from fusing. http://www.spondylitis.org/about/complications.aspx