I can try, but this is an advanced topic. I don't have a VR setup currently up and running, so I can't test this. It should work, but no promises.
Lines 275-346 handle gripping and moving the handle bar and its impact on the crane z-movement (since run speed is a 1-dimensional value it makes sense to use this object to control it, at least in my mind).

Of those lines, only 339-345 deal with the actual crane movement. If you replace them with something like this
double exponent = -handle.rotation.x / 16;
runspeed(Math.pow(2, exponent));
the handle bar should then control the speed (between 1/32 to 32).
Removing all the other control code for the other interactive objects will leave you with the user command code as in the attached model.
You'd need to copy all user commands, the "Handle" object (the thing you will grip in VR) and the "HandleDraw" object (the custom object I highlighted in the answer, copy the treenode from the tree, add a new treenode to the tree of the other model and paste this in there) to the other model. Add the "Handle" global variable and make it be a tree node variable that points to the "Handle" object.
runspeed-control.fsm