On brightness: supposedly, there are apps that can reduce brightness far below the normal minimum. I've not used them, but they have good reviews. Try something like this: Screen Filter
On battery life: When browsing the web on wifi, my Nexus 7 gets about 1 hour per 7% battery, which seems excellent to me. Is yours comparable? If not, try installing a battery statistics app to get details on what's draining your juice. Common culprits are bad network connections (wifi or cell data), apps that do a lot of syncing to the cloud, and apps that constantly wake up to check on something.