I respect you a lot because I can see myself in your post.. I was right there with the same questions as you.... and not so long ago..
Here is what I believe to be correct..
DNP does NOT prevent ATP synthesis. In vitro, sure.. However, in vivo is another story. If you measure ATP levels in cell culture before and after adding DNP, you will see ATP fall dramatically as the cells die. This is not what happens in real life though. The biochemistry texts from which you are drawing a lot of your information are based on in vitro observations, not in vivo. In reality, DNP doesn't change ATP concentrations that much. It only makes the process of producing ATP more inefficient.
Also- upon digestion, fructose is first converted in the liver to glucose via gluconeogenesis, and then exported to the brain... This is how it 'helps'
Andy