Now your throwing parts at it.
Take a deep breath, draw out the possibilities and check 'em.
You saw smoke so something got very overheated. That requires current, specifically more current than a wire or connector was designed for.
1. You can do what 67Dart273 suggested - look for the overheated wires and connections. I would do that.
2. You can also check the for continuity and resistance. I would do that too.
Facts known.
a. Occured with key in Start position.
b. Overheating occured in column
c. There is a connector in the column & connectors are often weak points.
d. Starter did not turn over - possibly because it wasn't getting sufficient power. (Knowing how the starter soleniod was jumpered would indicate whether there was a short, an open at the relay or the relay was not getting power from the start switch.)
So think about the facts.
Where was the power coming from?
Since it only happened with key in Start;
power clearly was making it to the start switch.
but was it going to the starter relay and ignition, or was it going somewhere else?
Current flow with key in start (not showing the seat belt warning system).
View attachment 1715580234
So is there a problem at the switch?
Put the key in Start and check for resistance between the power feed (J1, 12 ga Red) and each output position at the connector.
Should be 0 resistance at Start and Ignition start.
Should be infinate resistance at the others (unless the seat belt thingy gets power from the switch).
View attachment 1715580243
Now if you suspect cross wire short to the turn signal switch, you can check that too.
View attachment 1715580245
If everything there checks out visually and with your testing, then keep looking for the smoking wire.
It could be the relay wire S2 was grounding or shorting to the chassis or another wire.
It could even be a short to chassis within the starter relay.