Fusible links are like any other fuse, when they go they are gone and you can tell by the melted wire that is the fusible link. I dont remember what size is needed in that application but it is on the wiring diagram I believe.
Ghost problems like starting and running and then not are typically indicative of several types of issues;
- loose connections (coil, starter relay, starter, main power wire in the bulkhead connector)
- corroded connections (same as above)
- bad coil
- broken wires that are not completely broken; meaning there are a few strands still connected (same list as above)
You really need to take an organized and methodical path on this, start at the ignition switch and move through the bulk head connector to the starter relay, etc. stick with it and you will get it figured out.
one thing to take a look at is your distributor, look at the wires and connector first, pull the cap and look at everything inside to make sure nothing is broken, loose or bad.