Well, since sweetypie16 brought it up......yes, Parelli would definitly help you! lol.
Anyway, in situations like this you need to use a one rein stop. I would keep using the snaffle. I personally hate kimberwicks and would never ride a horse in one. If the horse "doesn't listen" to a milder bit, then he's become hard in the mouth, and this is due to the rider. Sometimes we may never know why a horse spooked or bolted all of a sudden, and it doesn't matter. Using 2 reins to stop a horse actually gives them power, but using one rein will take all that power away. It's much more effective.