I really think you should look at allears for menu prices. Saying you want to eat a few sit down meals doesn't help all that much. You can do a few cheaper meals for $40 for 2 people, or you could do signature meals with apps and desserts and run $100+. You'll have to figure out what meals you're interested in doing to get an approximate price.
I think you also need to keep drinks and snacks in mind. It sounds crazy, but we spend about $40/day just on drinks for 3 people. Bottled water and soda runs almost $4/bottle in the parks. We don't drink the water fountain water in FL and although you can bring in your own bottles in a soft sided cooler or backpack, I personally don't want to carry around like 10 bottles all day. And there's so many yummy snacks that even if you're not a snack person at home, it's hard to resist in the parks!
As far as souvieniers go, I'd say your amount is high for just souvieniers, but probably about right as an etc. amount. It can cover your souvieniers, anything you accidentally forgot to pack, an extra sweatshirt or rain poncho in case it downpours, and any extras, like renting a car for a few days, mini golf, renting watercraft or bikes at your resort, etc.
And as someone who goes for 2 week periods of time to Disney World, I don't think it's too much time at all. It's so nice to go at a leisurely pace and not have to worry about rushing in the parks. We have a few rest days and then if we're tired, we can sleep in in the morning without worrying about rope drop and getting everything done. It feels more like a vacation to us.
I also want to point out that I think you're smart not to plan on there being a
free dining or discount promo. With parts of the new fantasyland expansion slated to open in late 2012, it's possible that will draw enough interest that they don't need promos. Of course, it's also entirely possible that they will still need the promo, but like you said, better to let it be a welcome suprise, than plan on it and have to scramble for extra money if it doesn't happen.
Good luck with your planning!