Isn't there some sort of certification requirement that specifies that knobs, selectors and such, to the extent possible, should have "up" or "forward" meaning "good", "fly", "go faster" and "down" or "back" meaning "bad", "stop", "land", "go slower"?
No. You'll find quite a disparity between makes and models, and even the same type aircraft from the same manufacturer where different customers have different requests. In some cases, the switch positions can be exactly opposite...even on the same model aircraft.
Plus, if you want to do something that might be really stupid in-flight (such as shutting off the fuel completely), shouldn't there be some sort of guard so that you cannot do this by accident?
Not necessarily. Otherwise we'd have a lock on the mixture (some have a quasi-lock with a vernier control, others a simple metal tab, others none). Locking out the fuel shutoff could hurt or kill you in an emergency.
The first thing that should come as an automatic response is to unload the wings.....push forward hard. The article makes a point of stating how much you actually have to push, and the amount of horizon which fills the screen - it varies for each aeroplane but rule of thumb is that you go from 2 thirds sky filling the screen (on climb out) to 2 thirds ground filling the screen (at best glide).
This is unnecessary in an engine out or in a stall condition. The aircraft will continue to descend at it's trimmed airspeed, in fact. In most light airplanes, your climb speed is very close to your glide speed. If you're trimmed for the climb, you're trimmed close to the glide. In general terms, your best glide speed will closely approximate your sea level best rate of climb speed (Vy), and your minimum sink glide speed will closely approximate your sea level best angle of climb speed (Vx). If you're trimmed for one of these speeds on the climb, a power loss will result in a trimmed descent at that speed if you don't get involved (i.e. pulling back and interfering with the airplanes ability to do it's job...remain stable).
Inexperienced flight instructors scare students by teaching agressive pushing in stall training; it's not necessary. The difference between stalled and not stalled is less than a degree in angle of attack...something you can't see. If you're holding back pressure to stall the airplane during practice, for example, very slight relaxation of the back pressure is all it takes, and you can recover easily enough with the nose on the horizon...no need to fill the windscreen with sky, or ground for that matter. Likewise during an engine failure; you're entering a glide, not divebombing the enemy. Don't get in a rush to be too agressive with anything.
So far as preventing a spin...that's preventable by continuing to fly the airplane. Don't let it spin. Airplanes don't spin on their own...they need to be shown the way. Don't do that.