2000 Chevy Impala electrical wiring and computer issues

Two days ago the message center started flashing “low fuel”, “battery” and “security” and keeps rotating the same thing over and over. I was checking for blown fuses and loose or broken wires and saw that the main engine wire harness that plugs into another holder looked as if it was loose. There is a bar that locks them together and I pushed it the wrong way and it came apart. I put it back together and snapped the bar to lock it, now I can’t get the car started. Prior to this the fuel gauge stopped working, the cruse control stopped working and then the air bag picture came on. I am looking to know what the connection is between the harness coming apart and the car not starting and what I can do to get to the bottom of the message flashing, the fuel gauge and the cruse control not working. This has all happened the last week and a half.