1989 VOLVO 240, automatic - The car ran rough when I started it today. Tried to go anyway. 1/2 mile of rough running and the car died violently at stop sign. Died violently several times trying to get to side of road. Idled rough but ran. Pulled #2 wire at distributor and car ran good enough to get back home. Timing at crankshaft and cam shaft appear OK. Then removed distributor cap and saw arc marks after the posts inside the cap, worst on #2. I am sure to the more experienced this means something obvious, but I haven't experienced it till now. Then the wife tells me it was backfiring and running rough for a while. Any suggestions or better yet the correct answer would be appreciated. Thanks in advance.

Carbon tracking is not too unusual in higher mileage distributor caps. The conductive material wears, and a current path is set up from the terminals to ground. You should be fine with a new cap and rotor.

Once started it gets worse and worse, as it cuts its own track.

Years ago people used to carefully grind out the tracking marks and then varnish it, but the only sensible thing is just to replace the cap and rotor.