The endoscopy sounds like a really good idea - I hope the medics can treat if they find anything unusual 🙂
The symptoms seem unusual that you describe, and Im no doc or medical person (I am trained in allied health), however I wondered if it is worth asking about neurological origins, like nerve root compression in your neck or some other peripheral nerve issue like autonomic neuropathy?
I was formerly a sleep tech (the person who did the overnight sleep studies and reported the findings back to the pulmonologist/cardiologist) and there was always a wide array of sinus, throat, and symptomatology (including headaches) that I would record in the interview prior to testing or titration (where I would see what pressures and types of air delivery were needed for a person to maintain airway patency and adequate SpO2), which I would then contrast with morning findings using the same interview and score, to which I would provide specialists.
I dont know if you have done a recent (high quality) sleep study and if not, if it is worth undertaking, along with a head CT or some sort of investigation to image your areas that are causing problems? I can say that in the years I was working as a sleep tech, I saw a circular influence of sinus/other issues contributing to obstructive/mixed sleep apnoea, which would then exacerbate the sinus/other issues...all getting more symptomatic and disruptive over time (and the requirement to help was an intervention that broke the cycle, to start with, so to speak).
When it comes to managing multiple conditions that may or may not be linked, all being managed by different specialists that can remain siloed in their specialty at times, it falls on the patient themselves to work out the best form of care and the pathway to follow to get there.
I used to make a chart with the issues/medical problems across the top, and list the symptoms underneath each that may be related to it/occur due to it, and then see which ones were common. I then would grade them in terms of impact or loss of function, therefore which were priorities to treat. Then, I would see which medical problem had the most impactful symptoms, and which symptoms I should try to address first. By knowing which medical condition, I could then approach the correct specialist, in terms of priority and symptomatology of greatest concern.
I hope that might be helpful?
I wish you all the best, and I hope your medics can work together to figure out the root cause of this issue for you 🙂