Could benzodiazepines be stored in the brain and body fat, causing long-term sym

Yes. Benzodiazepines are stored in lipid cells (fat cells).. The only way to really remove this stuff is to just wait for it to be removed naturally..

You could start up an exercise regime that will start burning fat and increasing your overall metabolic rate.

There are no ways to completely "rid the body" of this stuff quicker than this though.. Sorry.