What structure likely contains the abnormal calcifications?
Most likely the superspinatus and infrapsinatus tendons/musculoteninous junctions. Alternatively, given the closer proximity to the acromion than the humerus, these may be in the subacromial-subdeltoid bursa.
What is causing the abnormal glenohumeral relationship?
Given the absence of trauma, this is most likely due to a large glenohumeral joint effusion with or without SASD bursitis.
There is extensive calcification within the subacromial space which is homogenously dense and amorphous in shape. The humeral head is displaced inferolaterally with a widened glenohumeral joint space and acromiohumeral distance, likely due to effusion.
It is unclear whether this calcification is intratendinous with a large underlying gelnohumeral joint effusion, or in the subacromial bursa above the supraspinatus inciting an intense inflammatory reaction and bursitis, subluxating the humeral head.