Is there any way at all to avoid sharp shadows in Bryce? In the Bryce world with all its lights as point sources it always seems to be bright sun, never dull and overcast with all the sky roughly equally luminous.

You can put a dim light next to the object so the shadow from the sun will not be as sharp.

I always duplicate my spots and offset them a bit. That way you get softer shadows. Don't forget to halve the intensities and adjust the falloffs.