The book says you need 8 hours of sleep a night. Failure to do so causes psychological symptoms- it will highly aggrivate your condition for starters.
You'll also not be able to think clearly, and will have a much higher risk of accident.
The best thing to do though is go by what feels right for you. I found by experiment that precisely 7 hours and 45 minutes is the correct amount of sleep for me, as that is when I tend to naturally wake up and I feel the best. More than that and I won't wake up right away, I end up drinking way too much caffeinated beverage. Less than that and I am not in my best condition, also ultimately resorting to caffene to try and stay focused.
Also the 8 hours or so needs to be continuous. While you may think that you can economize it by doing it in two or more sections, it loses it's effectiveness that way.
No wonder you're always feeling horrible and why you have some of the problems you have. This weekend go to bed at midnight, and try to wake up around 8AM- you might notice that you'll naturally wake up somewhere around then after a couple tries. You'd be amazed how it feels, and you should adjust your schedule for the rest of the week to give you about 8 hours as well.