Prednisone works one of 2 ways for CHer's for a very small percentage, a pred taper will actually abort a cycle, neither your boyfriend or I are lucky enough to fall in that group. For us, the pred masks the CH while we are on it, but if you go off the pred with nothing else to block it, they come back with a pissed off vengeance!
Your Verapamil dosing is not that high relative to others, some go as high as 960 mg a day to get relief. That being said, DO NOT GO TO 960 MG'S!! As mentioned earlier, you go up with verapmil slowly while being regularly monitored to keep the blood pressure issues in check. The sexual side effects are common with Verapamil, we joke about it a bit around here, like the pain isn't bad enough you have to take THAT away from us too!
Time to start getting yourself educated. 32 years of this stuff and my best success has come from a 2 pronged approach, it does not cure them, but it makes life very manageable.
1: A good prevent med. You seem to have that with the Verapamil, although it's time to get back to the doc and adjust dosing up. As mentioned earlier, I use lithium. If upping the dosing doesn't help, talk to your doc about adding lithium, the combo has worked for some when either alone did not. A loving and caring smack upside his head, stop playing around with the pred as the long term harm can be pretty severe.

2: Abortives......this is what your boyfriend doesn't have and desperately needs. Oxygen should be his first line abortive. An attack starts, I huff pure oxygen for 6-10 minutes, the attack is gone, I am pain free. It's that effecient and that simple. Read the oxygen info link on the left and ask questions. What area are you in? Someone may be close by who can help.
Imitrex injectables work as fast as oxygen but are expensive and i hate how they make me feel. Some use the imitrex nasal inhalers which are much cheaper, I have never tried them.
You'll read that a lot of people are chugging energy drinks to abort or reduce hits. I use them too, as mentioned earlier, he should NOT until he gets this whole verapamil thing figured out as you shouldn't combine the taurine in the energy drinks with the verapamil.
A lot of info I know but you both have so much to learn. CH sucks.

But with a little bit of work, you can keep beasty under control. Drag him onto the board so we can get to know him. We're a tight family and can't stand when one of our own is getting hit like this.
Joe
PS: One more thing. It's the weekend so I suspect he can't even call a doc until monday. Go to Rite Aid or Walgrens and get the following supplements:
Zing, Magnesium, and Calcium Citrate with Vitamin D. Take one of each, 4X daily, washed down with fresh lemonade. This alters your arterial PH making you less succeptible to attacks. It's a fairly new theory here but worked for me this last cycle when I hit a high peak and even oxygen started to fail me.