Broke battery ground connection? Fix it!

Code 20 wasn't the fan relay, that sounds like some kinda coincidence. The ELD is built into the fusebox.

I don't know about pump compatibility. NOT replacing the filter shouldn't screw up the pump, but maybe the filter IS plugged? Won't hurt to replace it, if you don't want to measure fuel pressure.

After it runs 20 seconds & dies, will it restart immediately? If not, check for spark. Don't just automatically blame the coil unless you see there's no spark.