Ehlers Danlos Syndrome (EDS) does create somewhat of a “loose spine” but you must be sure that you do not have other disorders independent of EDS. Mid-thoracic pain could also be derived from Scheuermann’s disorder (see website) or even a herniated disc.
I assume you have had standing X-rays and an MRI to rule in or out the above noted conditions.
The rubber mobilizer should be OK to use. This will help reduce the increased kyphosis that can be associated with EDS.
Shoulder subluxations are not uncommon with EDS. Strengthening the shoulder muscles can help.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.