First be sure that your scheduled month coincides with the seasons for the things you want to hunt and fish. I know it may sound dumb to a backpacker, but you can't just shoot and eat whatever typically. It'll need to be in season and you'll need proper license.
Two squirrels or two rabbits will feed you both for a meal. You said you're experienced backpackers, so I assume you know about all the dried foods that you can just add water too? If not, look into those. That is how I keep down on weight.
1000 rounds will be plenty. But practice before, get so you can confidently hit what you're aiming at.
If done right, this should be a fantastic trip. I'm jealous! Good luck!
-Jake