Low charge to no charge issue pulling hair out

Removing the connector engine side. question on the main harness plug on firewall
I think the '73 e-body is similar connector but would need to see it to say for sure.

Discussions on cleaning here:
Cleaning bulkhead connectors
I like these but they only can get accessible surfaces.
Plus electric cleaner, I use both Deoxit 05 or stronger and CRC quick dry depending on the situation and what I have available.

The failure locations are often at the wire crimp and insulation support.
You'll need a flattened cotter pin or something like that to release the female terminals