Picking the number of levels required for surgery has to do with both the pathology at the level and the symptoms the patient has. By your description, the problems lie at the C6-7 level and the C5-6 level is either not causing significant symptoms or is non-symptomatic. If the C5-6 level does not need surgery, it is not likely that it will in the future but without reviewing the images and seeing you, there is much speculation here.
Dysphagia or difficulty swallowing is not uncommon after an ACDF surgery but in most patients, disappears within the first month.
I cannot comment on a risk of paralysis without seeing you as a patient.
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.