I think what he needs to do is talk to his instructor, tell him straight away there's no possible chance for him to be ready for a deco course, and then list all the reason why this is so.
Then he and his instructor need to sort all this out, either on an intro to tech style course or some other simliar 'baby steps' program. Either way it's required and will cost time and money.
After getting a reasonable gear configuration and a little knowledge of all those valves back there and what they're doing, get some surpervised dives to help with the inwater steps.
Only after that, plus possibly a fair amount more experience dives with doubles would he possibly be ready for such a course.
You have to learn from somebody, and drawing conclusion based on your own mental wanderings is quite a pointless waste of time. There's little sense or need to remake the wheel at his stage in the game. He needs professional hands on help, and it isn't going to happen in cyber space. It's just not that kind of sport.
He's doesn't know enough to make a comfortable decision, what would he know? Well, ignorantly comfortable maybe, but reasonable and wise? I wouldn't bet on it myself.
That's about all the help in cyber space I can give him.