Time to remove and repair, possibly replace, under dash harness

hotrod swinger said
Where can I buy the terminals for the bulkhead connector?
Im in British Columbia.

Most likely will have to mail order. Some sizes may be available at an automotive store or a big electronics store.
Sources for Chrysler type wire terminals

hotrod swinger said
a jumper from the alternator to battery,

There's another possible explaination why the fusible link didn't go first.

hotrod swinger said
The connections honestly aren’t that bad. That was the one part of that section that wasn’t melted. The wires were fine from about 6 inches out from the bulkhead. The connecters actually look good. I can pull them apart and clean them? Possibly re-solder them?

They were never soldered. They are all crimped.
Using open Barrel Crimpers: A bit of Wiring 101
also a discussion on Lets Talk Open Barrel Crimpers - Reviews and Discussion

There's also a pretty good search engine here.

I'll recommend these two:
1969 Dodge Dart - Engine Compartment Main Bulkhead Connector

Cleaning bulkhead connectors

and for splices.
Inline wiring splice clips........from the Dodge RAM service manual

I think wire is covered in the Chrysler Connector thread.
Under the dash, automotive primary is fine.
For hot, fuel, oil or salt and moisture, marine grade or SAE TXL, SXL or GXL should be considered.
Marine supply often have a wide variety of insulation colors and will sell by the foot. or maybe in BC by the decimeter.
Rhode Island Wire has a lots of insulation options.