The vitamin D regimen has helped lots and lots of people: https://clusterbusters.org/forums/topic/1308-d3-regimen/
Many people find that they have to go to pretty high levels with the verapamil before it really helps: 960 mg/day, or in some cases even more.
The sumatriptan injections can be split: https://clusterbusters.org/forums/topic/2446-extending-imitrex/
This site was founded by people who had been through scores of prescribed meds (and there are scores of things that can be, and often are, thrown at CH) and found that using psychedelic substances, often at levels where there are no psychedelic effects at all, was the most effective way to end cycles and even prevent them. This approach is called "busting." You can learn about that, if you are interested, in the numbered files in the ClusterBuster Files section of the board.
Let us know how the O2 goes. That can be a huge change, getting it right. If you have the wrong things, that is probably the fault of your oxygen provider. So if you have a prescription, that's probably who you should take it up with (unless the prescription was written wrong). As you might have read, to go beyond the basics to a higher-flow regulator and a top-quality mask, you'll probably have to buy those things on your own. Here's where you'd get the mask: http://www.clusterheadaches.com/ccp8/index.php?app=ecom&ns=prodshow&ref=clustero2kit
His neurologist sounds like at least s/he knows the CH pharma basics (verap, O2, and triptans). That is surprisingly unusual. If s/he is also caring, that's another big plus.