Yes in prep_hurt you can catch damage to prevent a user from dieing but I would use wcs.Command(<userid>).SaveLife(<amount>) due to health add effects some the internal dicts to increase the user's max health. (For urposes of the .Heal() command and .Regen() ect.)

Python is case sensitive so the value you need to return to get a user's speed would be

GeSHi (python):
wcs.Command(userid).ReturnDict('speed')

and this value will always equal the users speed as long you have been using the wcs.Command(<userid>).Speed(<value>) and wcs.Command(<userid>).SpeedAdd(<amount>) commands (which you should be using for WCSP )

~J3ff