OK. I can't help you on the science content (I did Edexcel) but the exam is only an hour. Try a paper (start at the back where all the
big juicy questions are and get your teeth into them while you still have the
energy (pardon the pun)), when you get too tired: stop. Then the next day or something, mark it and see what you got. Then after 3 or 4 days try another unit. Once you've done all the units (about 3 weeks) work out what you got in total. Then start all over again with a different paper, try and get further than last time and repeat (don't forget to eat sleep and rave though).
I'd spend a maximum of 2.5 hours on IT coursework a week. No more than half hour stints. And no going on TSR while you do it! The same applies for English coursework.
It' good that you've recognised that you need to drop Lit.
Of Mice and Men:
http://www.thestudentroom.co.uk/showthread.php?t=3620993 see the second post on here.
What will you be asked for Merchant of Venice?
Is there any preparation you could do for RE?