Understanding 2 unit yield from 1lb ready to cook chicken

I've always been taught that baking is a science when it is compared to cooking. Cooking is very much 'to taste' and very individual. There are not as many things that can go wrong with a standard recipe in cooking, and you have a lot more room for creativity. You don't have to look at baking as that precise. However, unlike cooking, where you can add or subtract from a recipe with no real harm to physical structure, that does not hold in baking. For examlple, if you feel that there is too much salt in a recipe, cutting back can (and most likely will) have a cascading effect through the ingredient chain. You have to understand your ingredients and the effect they have on other ingredients. That is what makes baking a more precise science.
And in terms of flour, it is often the most 'ranged' ingredient. Depending on flour type, miller, altitude, water temp. etc., the amount of flour in a given recipe is always a guide. Again, you have to know your ingredients. You will never see 'one and an eight cup plus 2 TBSP hard flour' in a recipe, because it is so variable for many different reasons. Flour and water are the two most flexible ingredients, and are always variable. Hopefully this helps, I am sure someone will come along with a more scientific explanation for all different ingredients, I am just offering an experience based answer to your question. Also, you are right, do not mess around with baking soda and powder. If you do, you are asking for trouble. I would suppose that the rule of thumb would be that the more exacting an ingredient is (tsp, quarter tsp), you don't want to change much.

It means to combine the things listed up to and including the cloves, as in "combine ingredients 4 through 11". In that recipe it's just a helpful hint to tell you where the dry ingredients stop.

The recipe is already calling for ground cloves - it mixes them into dry ingredients as-is. When using whole cloves, if you don't immediately just grind them, you generally cook them in something liquid then strain them out later. (Similar to cinnamon sticks or whole allspice.) The cinnamon and nutmeg in the recipe are also ground, not whole. If a recipe wants whole cloves, it will explicitly say, and often count them: 10 [whole] cloves.