at this point I can basically park my ECV and walk around on crutches comfortably, but what happens on the physical ride vehicles? Do I carry the crutch onro the rise itself, or leave it with a cast member etc?
It will depend upon the ride. A ride like Haunted Mansion or Nemo, you can take them with you. On one like Splash Mountain or any rollercoaster, the Cm's will store them for you.