Adjustible clutch cable = THE problem.
You need a NON-adjustible clutch cable and a firewall adjuster. Grab a FORD "universal" clutch cable from Maximum Motorsports for like $75, shipped, poke it in there, and never mess with it again. Trust me, I've been there/done that with adjustibles AND aftermarket cables, and this is about the only one that's worth it for Foxes.
(Frankenstang can back me on this, the difference between her old cable and the new one was night and day.)
In the meantime, the rule for adjustment with cables is less slack in the cable = the clutch engages higher. So, if you have it wayyyyy tightened down, it will catch really high (or may not fully engage at all, which can lead to slippage and a smoked/glazed clutch); likewise, if you've got it too loose, it'll be hard to get in/out of gears smoothly and it'll catch with the pedal right off the floor. Being that you have a firewall adjuster AND an adjustible cable (totally redundant setup, really), you'll just have to play with it a lot to find the right balance.
With the cable turning with it ... what part are you trying to turn, exactly, that's making the whole cable twist? There should be a nut with a jam nut tightened up against it on the tranny side of the cable - loosen the jam nut first, then back the main nut off until you've got a decent amount of slack. Secure the jam nut tightly against the main nut again (it will work itself loose, otherwise), and take up the leftover slack with the firewall adjuster. Obviously, it's easier to make your adjustments at the firewall than having to crawl underneath the whole car.