I'll try, briefly...
Q102 - fuel cools the engine, both head temp and exhaust gas temp, so leaning will generally give a hotter engine. A very rich mixture gives a very cool engine.
Q525 - the 4 poles are effectively 2 Norths and 2 Souths, so it will do one rotation per 2 cycles of drive voltage.
Q571 - running on is usually caused by hotspots (carbon) on the cylinder head crown. If the magneto wire was shorted t ground it would never even start. An electrical cause could have been an OPEN switch wire, but conveniently this wasn't offered as an option.
Q583 - humidity will always decrease engine power, as far as I remember, but I stand to be corrected.
Q393 - no matter how wide the butterfly throttle is opened, there will always be some restriction, hence the manifold pressure will always be lower than atmospheric, even if only slightly. You must be careful to go for the fully correct answer rather than the one which appeals under ideal (impossible) conditions.
Q389 - I'd have to think harder about this one, but it will be something along the lines of: to maintain constant MP, the throttle is obviously being opened as atmospheric pressure reduces, but a greater volume of air flows to achieve this, possibly with extra fuelling, hence more power...
Hope this helps
PM