Wow, Hijak, I have something very similar! I experience:
*Tension at the base of my skull
*It seems to run from there to the center of my head to my sinuses
*Tight sinuses with constant slight-to-moderate stuffiness
*Seems to be connected to ringing in my ears (which is there any time I look for it--like now)
*Facial tension with an urge to grimace
*More pronounced when I'm tired or stressed
*My upper cervical vertebrae (primarily the "Atlas"-uppermost vertebra) always seems to need a chiropractic adjustment. This provides slight to moderate relief but only for a short while. When "Atlas" is out, the tension is worse and I find it difficult sleeping: shallow sleep; difficulty sleeping in; resulting fatigue during the day; falling asleep is fine.
I used to have painful headaches as a boy, into young adulthood. At 22, I learned Transcendental Meditation (TM). 6 months later, the headaches were gone. But this annoying tension has remained. When I meditate these days, my entire head loosens up. By the time I'm done, my sinuses have drained down my throat. The tension gradually returns during the next several hours. The only headaches I've had as an adult have been decades in the past when I've gone several days without meditating. I'm pretty regular these days.
In addition to meditating twice daily, I eat extremely well and maintain a very good exercise regimen. I drink coffee about 2 x per month and 2 beers per week. Yes, the beer seems to provide significant relief for about an hour or 2.
I am a psychotherapist by trade and clearly notice the discomfort/tension/stress connection both conceptually and experientially. I am aware of a small percentage of it being conscious. The majority is unconscious, i.e. the tension occurs "automatically." Depth psychotherapy would be extremely expensive and, to my understanding, the result for relieving this type of tension is doubtful at best. I've been thinking about trying biofeedback/neurofeedback which (to my understanding) provides a focus to the relaxation or brain activation/deactivation which might provide better and more durable results. I just have to pick myself up and do it.
I'm thankful to have found this forum. Keep the ideas coming.