You never need to use the barlow and the paracorr together - the barlow will make a coma free f10, so the paracorr will just be an expensive heavy thing in the way.
The paracorr does contain a 10% barlow in it too, but that is to push the focus out a bit so you shouldn't need to modify your scope to use it. (caveat you need about 10-15mm more in-travel to get focus. if your eyepiece is already racked in close to the tube, you may need to make some mods)
You are correct about the adaptor.
When you use a paracorr and a 35mm Panoptic, you will indeed need a truck battery to stop the whole thing toppling over and arms of Thor to pick up your eyepiece case
