Ignition experts needed

Sounds like everyone has said to do everything I can think of, except, try running another ground strap from the engine to the body. You can get one of those that clips on so it can even be temporary. Sometimes if you have a poor ground, it can cause all sorts of problems like the glowing tach light.

As for the starter relay, if it carried the bulk of the power, and had fallen apart or corroded, the remaining wires hooked to positive may have been carrying power to the electrical system and the heat from the excessive draw may have damaged something in the process.