I know for sure that they can go up to 100%, my mom works for the VA. We've discussed how frequently she sees CH diagnosis, especially since this most recent thing- she doesn't know if it's just that they are getting to the right age or if all of the head injuries are increasing the number. It can even be rated as service connected if you never had CH before getting in.
The number depends a lot on how disabled you are, and you have to be incredibly thorough and include as much evidence as possible that you have a problem. Chances are if you are disabled from CH you have other diagnoses that you need to include in your application too- things like severe depression, and EVERY other health complaint you have. If you are tired all of the time because of constant CH, then chronic fatigue, insomnia, etc. My guess is that either you are not being thorough in explaining your symptoms at the VA hospital so they don't understand how your quality of life has been affected, or don't understand how bad CH is. This is not the time to be stoic or a tough guy. Educate both of you, and find another person to be an advocate for you. Perhaps a doctor at the VA or I'm less familiar with Amvets, but they may help.
Years ago I posted a bunch of info on how to determine how disabled you are. I'm sorry, at the moment I don't have enough time to look for that info. It seems to me that I got a lot of it from about.com on headache disability and another group that helps migraine sufferers prove they are disabled. Find that info and thoroughly cover EVERY aspect of your daily life that is adversely affected by CH. If you have one headache every night for four weeks one or two times a year and that's your only problem, you are not disabled. You simply need to adjust your lifestyle to work it around your CH. If like the chronics here you have 8+ attacks a day, at varying unpredictable times, you can't sleep more than 45 minutes, you are struggling with suicidal thoughts, you've lost interest in everything because it's very hard to survive, you can no longer support yourself, you are disabled. The good thing about the VA is that as an organization they are set up to TRY and give you as many benefits as possible, but they can only do so if you prove to them that you need it. It sounds like you haven't. Try again, it's worth it.
*edited for typos and to add that I posted the links to disability rights info from About and MIDAS on my squidoo page, which I haven't updated in years: Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

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