If you want to make a dark map with a limited visibility range, drop all the eventing stuff, there are several scripts made to do exactly this.
I recommend Dekita's "Pokemon 'Flash' Style Lights" for this, or if you want a more serious and realistic looking light effect script, you can try Khas's "Awesome Light Effects" script.
Both goes well with Dekita's "Character Lanterns" script, which can make a simple lantern graphic in the hand of the character.
You already use a script, might as well save yourself from unnecessary and troublesome eventing and just get a cool script for it. :p