If you have a cold evap core but warm duct temps.....
"Turns out I didn't get fully engaged when I installed the box the first time.";)

Now, if the evap coil is freezing, below 32F, you have to test the function of thermostat (ice water in glass with salt, probe inserted along with a digital thermometer).
If thermostat tests good then simply relocate the thermostat properly in the evap coil.

A few days ago I confirmed that if I backed the thermostat switch off max, it did disengage the compressor

So, just thinking out loud, I can test the thermostat to figure out how cold it is when opening at max setting and compare that with observed core temps to see what the difference is and that way I would know roughly the core temp would be if I put the switch probe I the location I now have the thermometer.
It would be neat to figure out what the curve in the thermostat really is. I wonder ...

I don't know what 'curve' or correlation you are pondering,
however this is pretty simple:

1) Either thermostat turns off at near 32F. or it does not.
2) If the thermostat does work properly is it making good
contact in the evap core.

I'm thinking I'm still a bit overcharged too, right?

Haven't had time to fiddle with thermostat probe yet, maybe tomorrow.

I used a water bath of varying temperatures to chart out the thermostat knob's opening and closing points.

With pure ice water (T=33F) the switch did not open at all. At first I thought I might have broken the switch when I removed it from the evap core. I pulled the ice cubes out of the jar and started diluting with hose bib water to change water temps.

To take the data points, I started with the knob on "I" and slowly rotated until condenser fans activated (indicating switch is energized the compressor clutch, which activates my fans). Once activated, I then rotated knob back until the fans powered off.

As you can see, there is a ~1.5 knob-tick span between opening and closing points.


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