I'm wondering if he's capable of doing a lot of the things you guys are talking about. He might not be able to angulate very much with limited mobility. Upper lower body separation should be possible, just not at a 90° angle like I explained earlier.
Is there anything else that may help them with 1 inch of powder/crud? He says his skis get deflected to the side, which is why I think carving would help since it can then cut through. He also gets defensive in these conditions and ends up in the backseat.
The crappy rental skis don't help, but 1 inch should be doable. Tried it myself, it was just a bumpy ride.
doctor 1: "The patient is not breathing and his heart has stopped."
doctor2 : "What else is wrong with him?"
Good feedback for this so far. The skiing is so fundanentally problematic that crud will be tough as will powder and he's not young enough to muscle through it with inefficient technique.
As far as finishing turns on boring terrain well people do get good at this style. I've seen people drifting similar to this down White Heat at Sunday River which is quite steep. There's no incentive to do anything else till something comes along - like crud.