Mine's never been that bad, but I was having a lot of shoulder trouble over the fall and winter. Limited range of motion and it even got to the point of pec minor impingement on a nerve in my arm. I'm lucky to be able to afford an absolutely wonderful massage therapist, but with a Thera-Cane and some persistence you can work all those trigger points out yourself. This is the reference I use, which is the myofascial "Bible" for a lot of TErs, but the same authors have a book specifically about frozen shoulder.
I had trigger points not only in my rotators (particularly the infraspinatus, but all through them), but also all over the delts, pecs, SCM and trapezius. Once a muscle group gets that bad, all the surrounding and opposing muscle groups tend to become involved.
Hope you and your father both feel better.