Can you manually tune a choke? It may be a choke problem. I had a problem similar once, that it idled fine, but under load it just dropped idle. I fine tuned the choke, and it ran so much better.
Chokes are weird sometimes.
What I do is start cold (shut down at least 2 hours) with the choke pulled 1/4 way or more, and let it idle, unscrew the choke linkage, and move the choke flap back and forth until the engine sounds "just right". Then I re tighten the choke linkage. There are also guages for this, that measures the closure of the choke flap, but I think you can get it, and learn something along the way.
The reason I pull the choke 1/4 or more, because youre doing a "cold start", which requires you to pull the choke anyways. Youre just emulating a "cold start" by pulling it, and the engine IS a cold start. .By the time its warmed up (around 3 or 4 minutes), you can push the choke back in.
After all my mishaps and chaos with cars all my life, all my last cars from the last 6 years purred like a kitten...the Falcon purrs better than any other.
Its all an educational experience. What you learn and apply directly affects how good your car runs. Kind of cool.
Then I would say set the idle, b/c the choke has alot to do with the idle consistency, even at warm, if not tuned correctly.