Hi Cort,
I'm convinced a lot of sinus problems have structural origins. Many have reported better breathing through their sinuses after having gotten a treatment called atlas profilax--which repositions the atlas. I wrote this on PR a few years ago...
One man shared with me how he had such difficulty breathing, that he had to sleep sitting upright. Upon getting the AP, he was able to actually lay down and breath normally, and was able to sleep that night laying down in bed, something he had not been able to do for years.
In the past year, my brother has had such difficulty breathing through his nose, that it would wake him up at night. He tried
Serrapeptase, which helped some, but not a lot. More recently, he began applying DMSO to his skin regularly, and completely unexpectedly, began to experience much improved sinus function. My own best guess for his improvement is that DMSO is such a powerful anti-inflammatory.
You also might want to consider a treatment called "nasal specific" (has other names as well). This is where a balloon is inserted into the sinuses, and then expanded. It can not only significantly expand the sinuses and open up blockages, but it can exert enough pressure on locked cranials to get them "breathing" again.
I've had good success with all three of these therapies.
I might also add that I've gotten into the habit of doing various energetic exercises, one of which clears my sinuses every time I do it (couple times a day or so). Simply lay on your side(s), and massage along your spine the best you can. When I mentioned this to my Osteopathic doctor, he figured it was likely the result of major lymph areas along the spine releasing congested lymph fluid.