The megaproject will not complete until you complete those actions separately, although it may begin chewing on its own if it reaches the end of its cycle and the completion pre-reqs have not yet been done, although it will not be as efficient as if you had chosen to do them as their own actions.
Actually, what you need is for every major settlement to have a holy site to support the final implementation.
For a few more turns, yes. Hmmm... once there are no more shamans who worked directly with him (call it three generations/turns) his insights fade and the megaproject fizzles, the limited information becoming part of the People's mystical knowledge, but the possibility for more being lost. Each turn you wait after he dies also makes the total project length longer. You have Bynwyn for at most one more turn after this one.
Also, because you took Bynwyn, you got the requirement explicitly listed instead of having to blunder into them once the project was started.