Ok so u have continuity between the power wire and ground. Im assuming you have also checked for voltage on this wire? ;) someone has probably inadvertently used this wire for something its not intended for or the alarm has it grounded. Either way just bypass it with a similar gauge wire and see if it fires up. Shotgun diagnosis I know but since you dont really know the state of the engine other than what you were told Id get it running then go back and spend time tracing the affected wiring.