~ trail's end is by far the best value in WDW. i've never done the chicken meal you mentioned, but the regular buffet is only like 15 bucks a head, and is literally loaded with food. you just roll yourself on the boat back to the MK and hope it doesn't sink from the extra weight you just took on.
~ i've also done the extra bun mentioned above, and it works great.
~ don't forget that if you don't want the fries from a meal, just say you want the sandwich. all of the meals you see at counter service places are availabe a la cart.
~ plan a day to go shopping at DTD. and while you're there stop at goofy's cany company (attached to the earl of sandwhich) for bfast. no, you're not having candy for bfast. you can get a bagel, muffin, scone, danish, etc for only like $1.85. couple that with a coffee or hot cocoa at a buck, and you have bfast under 3 dollars
~ a great, cheap snack in the parks are the fruit and fruit cups. they're not only very reasonably priced, but are a great change of pace from the fries and ice cream that you'll be eating.