IAC seems incorrect. IAC only adds air. You should be able to reduce throttle opening slowly and bring vehicle below 1200 rpm where it should run correctly without sputtering.

If there are no codes then you've likely got a problem with an un-monitored system, or you have a problem with a sensor reading incorrectly.

Does the exhaust smell rich when vehicle isn't running correctly? Is there a large amount of water dripping out of the exhaust? Is the tailpipe black? Those symptoms generally indicate a rich engine which would often require higher rpm to overcome. As it's temperature based I'd be looking at CTS and the temp signal. Yes, it tested ok once. But this is an intermittent problem, yes? You could have a broken wire at the sender, or the pins could be corroded or misshapen. Or the temp scale could be skewed in the sender.

If there is no sign of the engine running rich but it stalls whenever throttle drops below a certain reading then you could have an issue with the TPS. That would show up as a distinct change in the voltage, and would likely need to be tested when the problem occurs in order to catch.

It's also possible you have a misfire or two or three. Moisture can condense in a distributor overnight and cause problems. A timing light connected to each plug wire could be used to determine whether one or more cylinders are misfiring but getting a visual of the cap during the time when the engine runs badly might be the only way to confirm it's moisture related. Any signs of carbon tracking or burn through could warrant replacement "just because."

I've had aftermarket O2 sensors cause problems by sending a voltage too soon after startup. Temporarily disconnecting the sensor or disabling closed loop would help eliminate the sensor signal as a potential problem.