Very complicated story, and I'm sorry to hear that your son has been going through such pain (and other issues) since such a young age.
Some of the things are similar to my story. I had a tumor under the skin on the side of my nose when I was 16 years old, and the surgery left the one side of my nose about 99% blocked. I had never had a deviated septum before, but when I finally went to an ENT to look into all this back in 2005, he said that I had a deviated septum and a lot of scar tissue blocking on my nose and leading to a lot of sinus infections, congestion, and I thought an increase in headache problems.
Typically, sinus congestion is a symptom of clusters (and actually of migraine, too - though not really in the same way it is a symptom of CH). However, even though the congestion is a symptom, I also felt that the congestion I was getting from the structural issues in my sinuses was ALSO triggering attacks. So I had the surgery done in March of 2005, and then another surgery in April 2005 due to very late hemorrhage after the 1st surgery. I felt absolutely miserable after the surgery, and it really was a rotten experience. I don't think there is any way around having sinus surgery being a rotten experience, and it truly does take a long time to feel better from it. I'd been told a year, but I never expected it to take that long to really feel like normal - but it was that amount of time! After a year's time, I finally felt like I could breathe normally and wasn't having as many headaches triggered by sinus congestion.
UNFORTUNATELY, it didn't knock away the chronic migraine I've had since 2001 or the chronic CH's I've had since 2003. That's because the sinus structural problems weren't actually the cause...
Now - neuralgia or CH is an interesting issue. Neuralgia/neuritis implies some sort of nerve damage to his supraorbital nerve - which could very well have occurred from his fall. CH affects the trigeminal (and supraorbital) nerves, but is not pain from damage - but rather a symptom of a series of things going on in the brain. (The real cause is unknown, but there are various theories for what drives it...)
Turns out, nerve stimulation may actually be helpful for both neuralgia and CH - so if he truly has tried everything and gotten no relief, then perhaps the stimulation will help, regardless of if the problem is neuralgia or CH. I actually have a bilateral occipital and right supraorbital nerve stimulator. I went to the pain center for a trial of the stimulator - but that was the only reason I went to the pain center. Otherwise I was managed entirely by my neurologist at the headache center, numerous specialists for other issues, and then the neurosurgeon is the one who sent me to the pain center for the stimulator trial. I had a lot of success with the stimulation, and got my permanent stim implant on May 13 of this year. Unfortunately, I am currently battling some issues with infection and the stimulator may ultimately have to come out and have a new one implanted in several months, but I must say it has truly helped my head pain.
What did the pain specialist say? I saw he has tried occipital nerve block injections. Has he tried a nerve block injection into the supraorbital nerve? It isn't a definite indication of whether or not stimulation will work, but a lot of times the docs want to try that before stimulation.
Anyway - hope that you find some answers for him soon. I guess you have to keep going through the various tests and specialists until all the pieces are put together. I understand that, as I've been to all different specialists looking for the answer.
It is good to have hope about the procedures - including the upcoming septoplasty. If it doesn't fix the problem, then you can keep searching - but it is always good to go into something with a positive attitude that it will help and work!
PF wishes and good luck!
Carrie