Hi Cupcakesprkls and welcome
You're a wonderful supporter doing so much to try to make a difference for your husband.
Batch is doing his usual amazing stuff covering off getting D3 to be an effective preventive. I'm someone who has been using this for multiple years with my last CH being six years away at the end of this month. So getting this working should transform things.
Relpax (eletriptan) and imitrex (sumatriptan) are both triptans which were developed to abort migraines, but can also be used to abort CHs. The exact way they work to do this isn't certain, but what they do is to make the blood vessels constrict, including those which supply blood to the heart (and everywhere else). Taking a very high dose of triptans, with 7-8 100mg tablets certainly counting as high, has the risk of causing problems. So as Batch has pointed out, reducing the total dose to 200mg or less, which is the advised maximum, is something he should do. And note that the 200mg limit is a typical one, the maximum for him may be different and will be based on his medical history. So he really should see a doctor to get personal medical advice.
I personally wouldn't take so many imitrex tablets. But knowing the pain of a high kip CH, I can understand how someone will do almost anything to make the pain stop.
The other problem with using imitrex tablets is that they can take 20+ minutes to take effect, which with the pain of a CH is a long time and a lot of pain (from personal experience). What works a lot better is either the injection or nasal spray versions which can work within 5 minutes. Do ask about getting these.
Batch has really covered off using oxygen well. There is also an oxygen info page - Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

- which has a load of useful stuff to know.
My oxygen kit worked wonderfully well on my CHs and it can be used as many times a day as is needed. It is something I won't part with.
The experience you've had with doctors knowing little about CH isn't unusual sadly. Most doctors, even many neurologists have little in the way of skills and experience on CH, which often results in them treating them like migraines. Whilst there are similarities, they are different. This is why we always suggest that people work with a headache specialist.
And don't worry about rambling when you post here. You've got an audience who have all too similar personal experiences and can totally relate.
One other thing he can do is using energy drinks, like Red Bull and similar, which contain both caffeine and taurine (check the ingredients list). If he drinks one of these as fast as he can when a CH starts, it can help reduce the intensity and duration of the CH. The caffeine acts as a vasoconstrictor (like the triptans do) and the taurine is a calcium channel antagonist (just like verapamil is, a common CH preventive).
Although it is probably best that he doesn't drink a can for every CH, but it is something else that he can use to help.
Be careful with using a pain management clinic and check that they have experience of working with people with CH. The answer to CH is not in managing the CH pain, which is beyond what painkillers can help with, but in preventing the CHs in the first place (D3 will do this) and killing off any CHs which get through (oxygen, etc.).
One other thing to ask your doctor is if he can use a prednisione taper dose as a short term preventive. This typically starts at about 80mg a day and drops off to nothing over 7-10 days. This can be very effective and will give him a bit of a break whilst the D3 gets working. But using prednisione for the medium / long term risks significant side effects.
I don't know how our supporters do what they do, seeing someone they love in such pain. You're doing great stuff.