Well, error code 38 is indeed the CAN line error. The usual suspect for this error is the ground connector to the body of the ECU, loose, corroded, wire broken/fracturing along its length at some point or otherwise the ECU body isn't being grounded. A second suspect could be corrosion of grime effecting contact between the ECU pins and its respective connector. Check and clean both ECU and connector pins. Otherwise wiring harness may be fuked somewhere?
Mate, you sure are having a time of it... Not wanting to state the obvious, however for the sake of any new readers or owners researching, make sure that any electrical work is preceded by disconnecting the battery first and foremost.
As Dutchie intimated, the immobilizer function is married to the dash/instrument cluster. If the dash recognizes the key, it gives the ECU permission to fire away. If the dash is changed, keys need to be programmed to it (unless a new set came with it).