bad misfire and ignition problem.

[1] Is it charging at 13-14v now? 18v is too high & may have damaged the ECU. This needs to be checked first.
[2] Do not see how p/up polarity could be reversed, as the plug/socket is keyed to prevent that. Reversed p/up is unlikely to run at all because it advances the timing 30-40* & is erratic. It can also affect rotor phasing, with the rotor directing spark to the wrong cyl.