Sounds as though have a failure of one of the main supply lines from the battery. You really need a circuit diagram to follow the progress of the supply, if you can check the things that don't work you may be able to pick up a non working line and connect it direct to the battery.

If you check the fusebox on the fuse that feeds the lights for instance, you should have a permanent 12v on some fuses, if its not there there is a fault between there and the battery, if it is, it must be on the switchgear somewhere.

It almost sounds like the car doesn't know it has an engine fitted After you replaced all these bits did you ensure they were all correctly matched electronically. It sounds like it's still immobised, I can't remember where the bit that pings the chip in the key is but I keep thinking of fuel pump and dashboard. You need to get diagnostics like opcom on it just to know where you stand.