Steering effort for manual 16:1 - should it be this high?

Dana67Dart said
IIRC there is a 20-1 box out there.

There are also quick ratio idler and pitman arms, (iirc with 16:1 box and quick ratio pitman you get 12:1 or there abouts)are you sure your pitman is OEM non quick ratio?

I am no suspension guru, but doesn't caster keep the car driving streight, which for autocross would not seem to be a need.

It helps with good steering return as well, which is also a good benefit to have racing. That's what causes the wheel to want to return to center. Positive caster. But, a lot of serious road racing vehicles do run very low and even negative caster. It all depends on what you're doing.