If the engine is running rough the rpm would be lower and could result in the alternator not charging enough dimming the lights.
There should have been more than enough clearance between reluctor and pickup that there should never have been any contact.
That is where I would start. Find out where the shavings have come from, and go from there.
On a side note, my dart started running rough and misfiring to the point I was stranded. I replaced the points cap rotor and coil. Nothing got better.
Had the car towed home, found the old (OEM side oiler) dist that had been on the shelf since the 80s, popped it in, set the timming by eye and it fired right up. Set the final timming and it has been running fine ever since.
The things I found were the dist shaft could move up and down about 1/4"
The old cap had a distroyed center pin. The rotor top had a circle of trace rather than a point where it contacts the center pin on the cap.
My best guess is that the rotor was moving up and down so much that the top of the rotor was not contacting the center pin continuously arcing and distroying the cap and causing the misfire.
Just food for thought
