I know how you feel HeadsAtCamp! I clearly have cluster headaches, but it is compounded by an issue my neurologist describes as something like cluster headache with concurrent aura migraine... basically, every time I get CH they also set off some fun vision-related migraines. He calls me his "most interesting patient." I'm not sure if that is condition or personality related, but I think probably a little of both.

He treats me for the CH, which also treats the migraines, so from experience I would recommend to you to demand to be treated for the CH instead of migraines. Topamax was bumpkiss for me. I couldn't function on that stuff for about 3 or 4 weeks after starting it and it barely helped (I'm being generous with "barely"). Also, your current doctor sounds like he has no idea what he is doing, so I would consider seeing a different doctor. These conditions are too painful for a doctor that a) has no experience with it, b) has no interest in learning about it quickly, OR c) has no sense of adventure in treatment.
My thoughts... if you haven't tried the Anti-Inflamatory Regimen, I would recommend you start. If you have a good response to Prednisone, it will likely help. I'm on AIR and it does the same work on me that Prednisone did without any of the side effects because it is vitamin based. That being said, it is not 100% effective for me (neither was Presnisone), although it has proven to substantially reduce the number of CHs I get (I'm down to 1 per day when I normally would be at 7 or 8 around this time of my cycle).
I just started Verapamil, so I cannot yet speak to its overall effectiveness, but I have noticed that it seems to make the oxygen work as an abortive where it didn't before. I think I'm going to request my dosage of Verapamil be raised from the 80 mg 3x daily I'm currently on and see if that stops them altogether.
Mygranal (an ergot-based nasal spray) does seem to help as an abortive, but that stuff is expensive! It costs me about $1,500 for 8 spray bottles with insurance ($150 if I hit my $4.8K deductible

)! I try everything else first, then use that as a last resort if nothing else works. I miss Ergomar... *sigh*
Stay hopeful, my friend! We must be the greatest advocates for our own health, so we cannot tire of trying new things. If you get tired, you can lean on your friends here. Someone is always willing to help you carry your burden. We know it's heavy!