For biology, make sure that you actually understand everything within the notes, EVERYTHING. The exams in biology test your application of knowledge, so merely being able to spew out information is not good enough. Do lots and lots of past papers, take your time in the first few, and then do the...
"scared that I might forget it" - are you cramming, or lack a bit of confidence in your abilities?
I have that paranoia as well, but it's to ensure that I'm as well prepared for my exams as possible.
The number of hours that you "should" be putting each day is dependent upon you to decide, and nobody else. You know what you need. Some may do 3hrs/day, some 6, and some 12. If you feel that the number of hours you're doing is rendering your study useless, then make some changes. Otherwise...
You put in a misadventure form stating reason why you fainted - e.g stress etc. You probably won't get a 0. You get an estimation based on your rank and your cohort's performance for that subject.