Like you diagnosis of affliction arriving over time.
Granted the neck muscle tension:
Have you considered "Rolfing"? A good rolfing practioner may be able to work this one through.
What is posture like? Is there good use of the tonus while standing/sitting? What is the muscle alignment like? Is there any tension further down the spine or legs? Is there any mal-alignment of the spine?
What are the feet like and is the gait balanced and rolling?
And lastly what is the teeth condition like?
Are there hidden teeth issues?