The removal of the schwannoma at L2 should have no bearing on your upper shoulder and neck pain. The feeling of “glass” in you foot could be from nerve injury secondary to the schwannoma removal but also could be from the spondylolisthesis.
Without significant compression of the nerves in you neck on the right side, the pain in your shoulder could be from Parsonage Turner syndrome (see website) or another type of nerve injury. You might consider an EMG from a good neurologist.
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.