Just make sure you get up super early the day or two days before your tourny, that way you'll go to bed early and get plenty of sleep.
It doesn't seem that your gonna cut any weight, other then like a pound if anything, so I don't think you need to drink more then normal. Just if your still training hard, make sure you keep up that water drinking. Losing 1% of your body weight in water can mess up your thinking, reflexes, gets you more tired. So just keep hydrated
If your drinking a lot of water normally, I don't think you have to worry about being hydrated the day of, you already will be, I think your nerves were just getting to you and playing mind games.
I know in the motocross when racing in the extreme heat, you need a nice drink every 15 mins, I don't think you'll be needing that.
Oh and try to put some fish, veggies and plenty of fruits in your diet.
You'll be fine - just keep us posted on how you did. I'm excited about doing my first tourny. I always feel like I need to learn more, but that will never stop so I just tough it out and remember those fist chokes