I suggest shutting the breaker, or disconnect switch off before you make the next adjustment. If the 'light switch' shut off was off and u still got a spark, it may be wired wrong, gone bad, or someone replaced it with a 4-way switch.
Steve's right about the breakers being able to hold for brief overloads. Might want to have a licensed sparky make sure everything is done properly before you get more than some blown up pliers while working on it.
