Are you running Full length headers? I tried theme with my Ron Morris clutch cable and it was too close to the headers. I used JBA shorty headers to keep the heat away from the cable. The system works well with Centerforce clutch. Contact Ron Morris he is very helpful.
I've got shortys as well. The Modern Driveline explicitly states it won't work with full length.
The biggest issue I had was installing the pedal mounted bracket seen in the first pic. It helps keep the cable straight while its fed through the firewall to the pedal. The bracket just doesn't fit on the pedal well - I ended up with it off center and rubbing the underside of the dash. I had to have a mechanic do some machine work and weld it to the pedal. PITA.
As for the header question, on the second pic you can see a silver heat shield. That is supposed to sit right where the cable runs past the headers.
I have broken one cable. It was getting hard to use before it broke and was smooth and easier new. It was not melted or bent. It just wore out.
I also replaced a racing clutch set with a HD Ford one, including a new cable, and it is more street able. I can get the HD one smelling hot with enthusiastic driving, but it will let me leave smoothly at stop lights. The X disc set was a bear to push and had no slip except at the tires.
Clutch disc and pressure plates are often sold in matched sets. So yes, the pressure plate has the hard springs on it, but referring to the clutch set is perfectly acceptable.