A camebak wasn't enough water for a 2 hour ride? How much did it hold and how hot was it that day. If you were bonking and dehydrated that bad from a two hour ride that you needed to crash for 12 hours I think you really need to put in a lot more training miles. I know that I usually don't even bother with food for a two hour ride or run and two water bottles would be plenty for me for two hours of riding. Most times I find I only drink one in that time. It probably helps that I trail run 1-1/2 to 2 hours just about everyday and do not take food or water. I drink before and after.
I usually don't tour with a camelbak, but when it is hot they can be nice and cool on your back if filled with ice.
A few suggestions for the weight thing...
1. You really need very little when on tour, most folks could leave half of the stuff in their panniers at home and still have stuff they could do without.
2. A whole pannier for food? I'd suggest buying food every day where possible and having very little more than enough to get to the next store, plus some calories for just in case situations.
3. If you wind up with over 30 pounds of stuff including panniers, but not food and water, I;d suggest going over your list and trimming. Not necessarily everyone's cup of tea, but 20 pounds isn't that hard to get to and 10 is definitely possible for the more spartan. Give that you ought to be able to get to 30 pounds base gear weight including baggage.
4. I won't go into specifics here, but check out my article on ultralight touring at
http://www.crazyguyonabike.com/doc/Ultralight You probably won't want to go as light as I do, but can still find a lot of useful advice there.