Sparks coming from starter

It sounds like a wiring issue but let's test it. Can you disconnect the wiring from the battery and the starter and then measure the resistance in the wire? You need a meter that has an ohms setting and you just connect the red lead to one end of the wire and the black lead of the meter to the other end of the meter. Then tell me what the resistance is or just get a picture of the meter.

Also, I want to confirm which wire started glowing. From how I read it, it was the battery feed wire or was it the black control wire?

I would say the starter itself is bad and shorted. That or the connection is shorted. That is the only way the connection would heat up like that. The power is getting to the starter and going into a grounded connection. I would probably pull the connections off the starter motor, then just connect a high draw test light like a headlight bulb in place to simulate the starter motor, kit the key and see if the light comes on bright. If it does you have power to the connections but the starter has failed. Not uncommon with parts these days unfortunately.

Sitting a while?

Key "off"

See if you can rotate the crankshaft at least two full turns with a ratchet or wrench in the direction it should turn.

If it's really, really, super hard to do or impossible, let us know!

The Medic