1. I don't see this mentioned as I glance through the advice you've received (it is mentioned in the long file I linked you to, but you might not have reached it). It will benefit him greatly not to take a full shot of Imitrex (if it's a 6mg injector). This shows how to split those doses: https://clusterbusters.org/forums/topic/2446-extending-imitrex/
2. I think it's fair to say that the only way for him to reduce the anxiety is to get the CH under control. And even then, there are lots of people who are very anxious during a cycle -- and even when they're not having headaches (particularly as the predicted time for a cycle to start is coming closer). They don't call CH "the Beast" for no reason: It's terrifying, ferocious, and unpredictable, and I don't think anyone ever forgets how hellish an attack can be, even when they have them more under control.
First, a functional note: He should take the calcium part of the D3 regimen about 8 hours from when he takes the verapamil. Can you tell us what the verap prescription is -- dosage and whether it's extended release (ER) or immediate release?
One thing that sometimes happens is that people with CH start some kind of treatment that they are told will help them, and then it doesn't help. That not only adds to the anxiety, it can also make them resistant to trying other things because they can't stand getting their hopes up and then being disappointed. I am generalizing here -- people are people -- but with his current anxiety and resistance, these might be issues. The verap is not going to help right away, and neither is the D3 (probably not going to help right away -- you never know). Usually verap is prescribed at a low dosage to make sure it doesn't have side effects, and the dosage is slowly increased. The D3 only takes full effect when there's enough of it in the system, though I think it has been shown that some benefits can happen pretty soon. So, a caution about anyone having unrealistic expectations about a quick fix. When the D3 regimen was first introduced, there was a whole lot of scoffing about it. But over time, it has shown itself to be very, very effective for a very large percentage of those who do it right. That's the basket I think you can safely put the eggs in -- if he sticks with it. If he has issues with it, or if he wants to reach out to someone, the popularizer of the D3 regimen, Batch (whose handle here is xxx), is amazingly generous with his time. Send him a PM and he will respond. He has helped a lot of people to do some tweaks that have shifted things for them.