The frustrating thing, at least for me reading this, is that somehow CH is not enough of a doggone disability. You should get a friggin medal and a lifetime pension from your organization for what you've accomplished while dealing with chronic CH.
This study looked into cognitive impairment in people with CH, but didn't find anything significant. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4354253/ Maybe there are other studies showing different things. An interesting sentence from it: "When patients were asked to rate the severity of their own cognitive failures, patients with CCH reported higher cognitive failures than the ECH patients, and statistically significantly higher failures than HCs." ("HCs" being healthy controls.) But it didn't show up on the tests.
You have done your homework, so I'm just gonna say a bunch of stuff that I feel pretty sure you already know. The one you don't know yet is the D3, which could be a game changer. Busting has been the salvation of many folks with chronic and episodic CH. A "last resort" that many wish they had turned to first. Do you know to try an energy shot (5-Hour Energy, for example) at the first sign of an attack? It can stop them, or reduce their severity. Batch says drinking icy cold water from a straw, aiming to create a kind of brain freeze, will help as much as the energy shot. Increasingly, it is being noticed that pollen worsens CH for most people. Many get some or a lot of relief from just taking Benadryl -- some every day, but more during high pollen seasons.
If your business on the road is by car, can't you bring a small O2 tank with you? If it involves flying, you can usually arrange to get O2 at a destination, through your O2 supplier. (Again -- apologizing since you almost certainly already know all this. No need for you to reply.) Many people get quicker aborts with higher flow rates (buying the higher-flow regulator) and from the mask made for CH: http://www.clusterheadaches.com/ccp8/
Is verapamil ruled out because of your heart issues? The required daily dose can go as high as 960mg, which is much higher than most people are typically prescribed. The zonisamide if of course another anti-seizure drug. We've had some people here from whom other anti-seizure meds, such as gabapentin, have worked well . . . but for most the side effects are rough ("problems with thinking or speech; trouble concentrating" are among them). Elavil/amitryptiline has been very positively reviewed by some folks here, at least in the short run (we don't generally hear back from folks who find something that works). As usual with CH treatments, mileage varies all over the place.