Twin carbs (e.g. twin DCNFs on a 1498cc X1/9 motor) are always romantic, but having experienced various single strangled carburettors on 80s FIATs, I believe the needs of reliability and economy have relegated carburettors to the history books...
Honestly there are so many symptoms mentioned in this thread that it's difficult to know where to start. I think I would clean the connector blocks behind the battery (and check the fusebox for evidence of water inside), then fully charge the battery, and clean/tighten the battery terminals. After that, it needs the fault codes read (or reset, then read again, as the connection problems have possibly triggered many false codes).
Hopefully there will be a fault code for the Engine RPM sensor - that would explain the lack of spark - this sensor is at the base of the engine block, behind, near the gearbox. Check it is connected before replacing, obviously.
-Alex