1) I bled the floor jack by using
this procedure. Another procedure for bleeding and filling is shown
here. I lubricated the moving parts, and the jack was already
full of oil. The jack raises the wheels to 10.5", the underbody to 18" high, and the jack was much more quiet than yesterday too.
2) I think the 10.5 to 18" height is high enough to work on the underside.
3) I'm not confident of the 1000# capacity of my dolly. If I decide to go higher, then I'll rig up a base to go under the floor jack.
4) Next I will look for places to mount the coroplast to the frame.