OP here - Profound thanks for all your thoughtful replies. I went to the gym yesterday and did Workout B, which includes a dead-lift and dumbbell presses (alternating arms). Out of curiousity, I went to the rack to experiment with squats. I didn't add any weight. Man, it was very painful. I found I kept pushing my hands outward - all the way to the weight stops (makes putting it back on the rack tough).

So tonight I grabbed a 4' wood dowel (broomstick diameter) and I just couldn't get it to rest on the back of my neck/shoulders. My shoulders just don't want to go back sharply enough to get them in line with the back of my neck. I had my wife (59) and son (24) try - no problem. Further experiments included spreading my arms and pushing back as far as possible - I can only get my elbows slightly farther back than the plane of my body.

So the problem is I'm deformed! And I will have to find a squat substitute exercise.