I was also going to mention adding a ground to wiper motor like geo said. I had to do that to my 1988. You can even test it by using jumper cable or any wire to go from a good ground to the case to see if it starts working.

If it' hasn't been said yet one quick way of pinpointing the circuit is to pull one fuse at a time and check with a meter there instead of at the battery.

Spot light wiring was a good idea too. The wire for them usually runs loosely inside the pillar cover and can easily get pinched or rubbed with a screw.