That's the thing! There is no one "solution". It must be a judgement call from the developers after weighing the factors going in and the tuning. What I was warning of in that paragraph was cranking the lever only down (or, only up, which is just as bad). That's less game design and more deal-making "We'll never frustrate you if you buy this game" or "We made this punishing as FUUUUUUUUUUUUUUUUUUUUUUUUCK, buy it!".
Read what Miyamoto was saying. It's very good.
I did.
I'm not really seeing how that relates to your argument. If anything, he's largely in support of the mechanic that SMB/HLM use; you die, you restart back at the level and go through the good and bad parts. It's just that they are tuned to be highly punishing (you have to move fast or one wrong move is death), yet highly forgiving (you restart immediately if you do die) to balance it.
Mario is going for an entirely different pace.