I agree that trying to figure everything out down to the different pieces of chicken is a waste of time. You need to know what the cost per serving is, so you have to start with the serving size. Is it 2 pieces, 3 pieces or 4 pieces?
If you case is 48 lbs at $1.28 per lb, then your total case price is $61.44.
From there, you should be creating a batch recipe and a plate recipe. The batch recipe helps you calculate the cost of the chicken portion of the plate. The plate recipe adds in your sides, bread, condiments, and Q factor (intangibles like fry oil, garnish, etc that have to be added to every plate recipe).
For your batch recipe, calculate the cost of frying a whole case of chicken IF you usually thaw and fry it by the case. This is much easier, and more accurate, than trying to calculate the cost of breading and seasonings for each individual piece. More importantly, you'll be including the cost of the breading and seasoning that gets wasted, which you have to recover money for also.
The batch recipe might include $61.44 for chicken, $2.50 for flour and $2.50 for seasoning, giving you a batch recipe cost of $66.44. Next, you need to calculate the yield for your batch. You can express this in "pieces" or "portions" (3 pieces for a 3 piece plate). If you only have one serving size, I suggest calculating a "portion" cost. If you have more than one size chicken dinner, calculate your yield in pieces.
To do it by pieces, just divide your batch recipe cost ($66.44) by the pieces per case (128). You'll get a cost per piece of roughly $.52 per piece.
Now you have to build a plate recipe. Add in the cost of everything included in the dinner, like cole slaw, corn, mashed potatoes, gravy, biscuit, etc. All these items should also have a batch recipe with a yield that shows how much they cost per serving portion or per fluid ounce. The serving cost goes on the plate recipe. Each plate cost should also include the Q factor which covers the cost of all condiments, cooking oils, etc. The only way to accurately figure a Q factor is to add up the total cost of all these items over a period, then divide that cost by the total number of plates served during that period. This gives you a cost per plate of all those items included in the calculation. Then, you can simply add in that amount to every plate recipe.
For pricing, please do not use your budgeted food cost percentage to calculate what you should sell the dinner for. Food cost percentages should only be used for managing, not for pricing. For pricing, you must consider every cost of doing business, and you must consider what your competition is selling comparable products for. Dividing by some arbitrary percentage to come up with a price does nothing to guarantee you'll collect enough dollars to pay for staff, rent, insurance, electricity, linens, chemicals and profit, which together can make up 55-80% of your total expenses. Considering only 20-45% of the cost of business (food cost) to calculate a sale price can lead you to underprice or overprice. You also can't expect to run the same cost percentage on all menu items. Some, you'll have to sell at a lower cost to compete, and some can earn you more profit while selling at a much higher cost percentage. For example, would you rather sell a hamburger that cost $2 and sells for $8, or a lobster that costs $20 and sells for $40? One earns $6 in gross profit and the other $20 in gross profit. There is going to be a lot more left of the sale of the second item after you pay all your expenses than the first item.