That is exactly the description that I needed! The fast idle cam can be "locked" either up or down if the rod and lever connecting to the choke plate are turned to their extreme in either direction. Somehow I was missing that these extremes should be avoided and that the fast idle cam should actually be hanging.
That problem is solved.
Next question is that on the choke side, there is a spring loaded cam all the way in the bottom rear corner of the carb. I found this image of it and circled it.
On my carb, that choke linkage lever (B) is not touching the cam spring loaded cam (A). I can see on my cam where it is worn as if they should be touching (or have been in the past) -- do I bend the tang on the cam so that it makes contact? If not, what purpose does that these serve and when/why/how do they make contact?