Good post, but with one common mistake: The front brake is still the one who provide more braking power in the dirt - same as on the pavement. Ricky Carmichael, for example, said once that the only thing that prevents him from going faster is the power of his front brake-he wished it could have more (not an easy statement from someone who rode with a Nissin works front brake..). To really learn how to use it...now that's something to practice on! No doubt about it though that the rear brake has a main role too, especially in "rear steering" for cutting corners (and other technics in motocross).
Off road ridin adds a rider in so many aspects:
-Throttle and clutch control, ofcourse
- Better use of your lower body
- A lot of movement on the bike which helps to understand weight distribution.
- Like u said, dealing with the "unknown" and panic situations- even a long straight could hold a lot of surprises on the dirt.
- Riding alot in the dirt helps to keep your body in good shape, much more than road riding (every one who ever got on a demanding trail will realize it in a matter of minutes

)
I learned over time though, that it's important to know what to take from dirt riding to the pavement. It's good to remember that on the typical sport bike, we r sitting with bent knees and very narrow hands span - this limit our movements alot, and make it impossible to save yourself from falling with your leg, for example, or an aggressive front slide like on soft terrain. There's is alot more attention to tires grip than in the dirt, and alot more importance for being smooth (especially on public roads).
But no doubt it adds tons of control - no wonder alot of the GP's riders do motocross even on their vacations. It's just a good useful training.