One thing I remember from Good Eats, whole eggs are drying agents, which tend to make them crumbly, and sugar, especially brown sugar, being hygroscopic (pulls in water) tends to keep them moister. These are the three recipes he did in one show. Thin and crispy, puffy cake-like, and chewy. Chewy vs puffy, chewy had one egg and one yolk, and puffy had two full eggs, and the puffy used a cup of butter flavored shortening, where the chewy used two sticks of butter. These are for chocolate chip cookies, but you should be able to figure out how to fiddle your recipe from there.
Wish the site broke out sugar... would love some oatmeal cookies I could eat.
It's going 'holy crap!' about your manganese (513% of the RDA) and sodium (192%), though.