For now I've 'solved' my joystick problem via getting a diferent, working joystick.
jstest-gtk shows numbers on two axes running from 0 to -32000
and [hid] gives me the same inputs, 'abs_x' and 'abs_y' as numbers in the range 0-256.
WIth jstest the numbers naturally take some big jumps, but seem consistent with the joystick motion.
With [hid] the values jerk about fairly randomly -- These are maybe the original numbers mod 256 of something?
Is there anything available to bring in the original raw data so I can put it into more linear order?