Glad you got it solved. These engines are very simple electrically. I had a friend with the same issue, I got him limped home with a stripped wire from 12v to fss. Good to know how to keep going in a situation like this. That connector corrodes over the years, then melts from arcing.
The red wire with a green stripe is key on power, it goes to the fss and glow plug relay I believe, and maybe some other stops along the way.
Another good tip, if your glow plug controller acts up stranding you, you can bypass it to trip the relay, or if you got a big chunk of metal like a screwdriver you don't care about, you can jump the relay. These trucks dont start well without glowplugs , some use ether instead but it's not recommended unless you disable the glowplugs. If one plug goes bad or has a bad connection the relay will get cycled rapidly by the controller spazzing out, not generating enough heat to start sometimes.