Take a look at the articles on the home page of this site in the left hand column, particularly the 27 pound, 7 day gear list. It's not that difficult!

Why do you carry so much water? Do you backpack in the desert? I backpack in the mountains where there are normally frequent water sources and rarely carry more than a half liter at a time. The exception is if I'm traversing a long high ridge, especially during a dry spell, and may travel all day between water sources. In that case, I will carry 2 liters to get me through the day. I of course drink at least two more liters morning and evening in camp. "Cameling up" at water sources helps!

Reducing the number of stuff sacks is a good way to cut weight. That "it's not that much" becomes significant when added up. Consider using zipered sandwich or snack bags for organizing small items; they weigh far less and you can see what's inside. For even smaller zippered plastic bags, try the beads section of your local crafts store.