The injectors fire in pairs, so if #3 is firing (I think) then there isn't a problem with the distributor trigger. If an njector fires in another position but not hooked to the #1 wire then there is some sort of fault somewhere. The control unit puts out 3 or 4 volt pulses of pretty short length - especially at idle, and can be very hard to catch with a digital multimeter. You might see the needle wiggling with a needle meter.

Check on eBay for another control unit. They occasionally sell there for not much money - they rarely go bad so the demand isn't very strong.