I have a bit of expertise with exams - decades worth. I recommend the following program:
Don't drink
Get off the sleep meds
Get off the Nyquil
Continue your snuff or Copenhagen
Get 7-8 hours of sleep
Drink tons of water
Study the content
Take as many practice exams as you can
Begin meditation for 5 minutes a day, in the morning and 5 minutes before you head to sleep.
With this recipe you cannot fail - give yourself plenty of time for the study portion.