Shut the flying tips off, they're probably causing the green banners.
Yes, that exactely the soure of the problem.
Concerning the engine shutdown, as already stated above, CRTL+SHIFT+F1 will put the mixture down to 0, so jet or prop, the engine will stop

To answer your question, hitting "M" key will select the magnetos. If you hit "+" or "-" after, you'll change the magneto position, so hitting "-" several times will set it to OFF, and you already know that.
Now, on a jet aircraft, if I'm not mistaken there are no magnetos. This is why hitting "M" has no effect and the "+" and "-" keys stay assigned to the zoom. Instead, you should hit "J", to select the Jet engines, but I'm not completely sure anymore, you should double check in the keys assignation of FSX.