The pass mark is so low (60-65%-ish) that I don't think you even need to know it all anyway. Goodness knows I didn't. Plus it's multiple choice, and good intuition and ability to make educated guesses will see you through lots of it.
Your Japanese already seems pretty great, actually. I don't think N2 would be beyond you, by what I've gathered of your level. You certainly seem a lot better than I was when I passed it back in 2008, anyway. :'D