You have a much better understand of the IAC then most people, which is great.
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However I pulled the IAC and the Pintel was not gummed up but I sprayed cleaner into the area in which the pintel goes.
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That is very risky.
Being you watched for and saw movement of the IAC pintle, the IAC is still working somewhat but it may not be moving as much as it should.
The IAC my be moving for some of the pulses sent to it but not all always moving for every pulse sent.
You can see the IAC count with many scan tools. When started cold it should show about a 150 count. If it does show a count of 150 and does not idle fast you should suspect the IAC is not moving as far as it should.
AT normal hot idle the IAC count should be under 50. I like to see them at 15-20.
You tested the coolant sensor at 210 & 70 but not colder then that which is where it is struggling to start. I would test it first thing on a cold morning. The coolant sensor is a common failure part. But so is the IAC.
It sounds to me like the problem is caused by one or more parts that are marginal in operation. The ECM on these trucks will not set sensor codes unless the reading is outside the range on the top or bottom end. A coolant sensor could read 85 degrees all the time and this system would not set a trouble code.
You should test the fuel pressure with it running. The TBI trucks have idle problems when the pressure is low. The TBI trucks have no fuel pressure test port.
Also see if the scan tool you are using will show the P/N (park – neutral) switch information. The ECM uses P/N information to evaluate where the RPM should be, which affects IAC operation.