Time to rebuild?

Your vacuum break may not be sufficient.

Sorry, I don't know what you mean by that.

A) the cooling fan disabled, and the PCV removed from the cover and the hole plugged, or

You mean remove the fan belt? How would that affect the crankcase? EDIT: Do you mean so that the fumes blowing out of the breather would be visible instead of being blown away by the fan?

I do plan to adjust the valves as soon as I get a chance. Then I'll redo the compression test. I think you're suggesting to do it cold just to make sure the temperature is the same for all of the cylinders? I believe last time I did it I rechecked 1 and 2 after finishing the others, just to see if anything changed as the block cooled in the interim. But I'm not positive I did that.

I've looked at the choke with the engine idling and air cleaner off, but I don't have a sense for how fully it should close and how quickly it should open at a given ambient temperature. Maybe I can post a video of it.