a) Students are supposed to do a simulated safety top in a pool, and they are supposed to do safety stops on their OW dives. What is an assisted safety stop?
b) Gas planning is part of the OW class now, but I agree it should be a big part of the AOW deep dive. Students should see for themselves how much faster they will go through air at depth.
c) That is in the OW class.
d) That used to be a standard part of the AOW. It was taken out a number of years ago, and I believe the reason was that the results were not as you state. With MOST of the students I had, they did BETTER at depth than at the surface, probably because their surface performance gave them practice doing a task they had not done in a long time. I tried other tasks, including give students a letter and having them give the preceding 5 letters of the alphabet in reverse order. Again, in MOST cases, they did either just as well at depth or better. There were many threads on ScubaBoard about this back in those days. PADI did not state why they removed that requirement, but I believe it was because students were getting the notion from their success at that test that narcosis was no big deal.