Hey there Talisman,
Blown engines probably means you've not opened your radiator, they'll overheating pretty Quickly if closed. Mixture lever on the Spit(I guess that's what you're flying) is either auto_rich or auto_lean, that's normal for that plane, check the flames coming from your engine, blue is good, yellow is bad. Prop pitch will cause engine revs to drop as you change it, though it will take bigger chunks of air so set finer pitch for max speed in level flight, that one threw me too when I first started to play. As for key mappings, make sure you click 'apply' when you've made a change not 'OK' otherwise it won't save the changes.
Let me know how you get on, oh and if you're having trouble taking off trimming your rudder full right helps!
Bokonon.