Was the car originally an automatic?
If so, you are prob missing the pigtail that plugs into the NGS on the t5, that clears the code 67, when trans is in nuetral.
If this is the case, you'll need to procure a t5 harness that runs from drivers kick panel, to the trans tunnel and out to the car. It will also replace the vss wiring if that's what melted.
Short term solution. On the clutch pedal are two 2-wire plugs. One is starter circuit and other is the NSS loop. Pull one of the plugs, and try to start car by pushing in clutch, if you can start it, then the plug in the switch is for the starter circuit. Jump the loose plug (NSS circuit) with a 5amp blade fuse for now. This should improve idle quality