Causes for soft cookies

I've been watching your discussion with interest. I'm sorry not to have any real practical advice, but your question has prompted me to do some web-surfing to learn more about the science of cookie-baking.

What I've discovered is that liquid is the cause of softer cookies.
Humidity is the number one factor. If it's hot and humid in your locale (and I assume Ohio is pretty much the same as Missouri), crisp cookies will soften up within hours.
How the cookies are stored is important. A ceramic or pottery cookie jar with a loose-fitting lid won't keep air moisture out. It's better to use a metal can with a very tight lid.
The amount of liquid used in the recipe will affect the texture. Be careful to use a fat that has as little moisture as possible. Different brands of butter and margarine have differing moisture contents. (The baker who publishes the site likes Land O Lakes over cheaper, store-brand butters.)

From what I've learned, I think Candy's biggest problem is the amount of brown sugar in her recipe. Brown sugar actually absorbs moisture after baking. White sugar makes a crisper cookie. I know for fact this is true because the oatmeal cookie recipe I use contains no white sugar at all, and it makes the very chewy texture my family prefers.

So in your case, Candy, what I would try is substitution of most of the brown sugar with white, using only about 1/2 cup of the brown for flavor. I'm not science-minded enough to guarantee you this will work, it makes enough sense to give it a try. Good luck!