I haven’t even begun to look at the cable situation in my Saab, but I know of this with my truck. The resistance of the cable doesn’t change per se, but the voltage carrying ability does. If one strand of copper in the cable is connected but the rest of them are broken-the cable will still read very low ohms.
If no one is making a new cable-the next best thing is a store or shop that makes audio cables for high power car stereos. They typically have gold plated connectors, high quality very thick cable. And can make it custom fit to length.
Next cheaper route is to go to something like Tractor supply and buy a spool of their 2 gauge cable and add your own connectors. Some stores have the ability to crimp on the terminal connectors.
What you wanna do before you get down this rabbit hole too far is do a voltage drop test on the cable itself. Go from the terminal to the end of the cable. Read voltage. Obviously it should be near zero but you’ll see it isn’t. If it’s above 1.2VDC, the cable is starting to fail.