80 mg of prednisone is a middle of the road dose for clusters. Generally one seeks the lowest effective dose 60-100 mg a day) to pause the cycle and maintain it for a week or two while you increase the verapamil dose (which most probably will be constipating so use a laxative and stool softener).
You will find the needed verapamil dose is going to be higher than you would think (up to 1200 mg for a short time in some instances) and blood pressure needs to be monitored to avoid getting dizzy.
Long term exposure to high dose steroids (months or years) have potential serious side effects which need to be monitored closely by someone familiar with managing high dose steroids. The emotional toll of high dose steroids is also not insignificant and needs to be monitored usually by someone who is close enough to you to notice a mood change.
If you have been on prednisone at 60 mg a day for a couple of years your concerns are justified. Short bursts of steroids like prednisone do not require a taper but if you have been on 80mg for most of 2 years weaning off might be a challenge and the guidance of an endocrinologist or rheumatologist knowledgeable in this is justified. The prednisone can suppress normal communication between the adrenal gland and the brain and tapering off oral therapy has to be done in such a way to allow your own adrenals to start functioning normally. Also if you have been on prednisone for a long time and then are under increased stress (surgery, injury or intense life event) you actually need a boost dose of a steroid to handle things physiologically.
Prednisone and verapamil can be helpful in busting a cycle but try and wean off as sensibly as possible using O2 as a abortive. Once you are off roids, verapamil and other blockers for a week consider another trial of MM in the correct set and setting with a knowledgeable sitter. Sometimes when you get wrapped up in a menagerie of modalities it takes a while to refocus and follow a disciplined path (which, of course, will always have detours)