Problem solved - I think(!)
Picking up where I left off a few days ago, I let the car get up to temp before making any mixture adjustments. Duty cycle read ~92.3%.
Turned car off, turned mixture 1/16 of a turn back, restarted car (it was a little harder to start), let idle stabilize for a minute or so. Duty cycle again settled at ~92.3%. Another 1/8 turn back made it even harder to start, and again the DC settled at ~92.3.%. As a number of you suggested, it seemed to be very lean.
So I turned 1/2 a turn clockwise and DC went to ~30%. I backed it off a little bit (1/16 of a turn) and got around 36% DC, with a lot more DC fluctuation than earlier. Idle seemed a little better and starting was easier. A couple more tweeks and I got it to around 45%. Idle seems pretty smooth and it starts easily.
Well, I think the problem has been solved (fingers crossed). I'll know for sure tonight when I take it out for a 100 mile trip.
Thanks again for everyone's help - and especially your patience and encouragement. I feel a little like a total novice.