First lines of the first post of any thread should be:
- What year
- What model
- What engine
- What transmission
- What recent electrical and/or mechanical mods.
That being said...
You have some high resistance connections in your ignition switch connector resulting in melted connector and wires.
The missing ground connector in your wiring harness connector is not an issue.
Later model vehicles that use the same ignition switch have a ground wire in the harness. Aftermarket adds it to the switch because it makes the switch forward and backwards comparable to a larger base of cars.
You need a good wiring diagram
Mymopar.com has many, free download.
Classiccarwiring.com has laminated color coded wiring diagrams around 25 bucks best 25 bucks I ever spent.
Then you will have to start tracing out circuits and find the fault