I did aircraft refueling for a while earlier in my life. Yes, AvGas isn't used for most military aircraft. Certainly not for helicopters or combat aircraft. JP4 is the fuel of choice. And in general terms, yes it is like kerosene, though JP4 is much more refined...less dirty.
So the reason you can't run anything other than JP4 in those engines is due to the residue left over from the intense burn temperatures of those engines. While, technically, those engines would run on diesel, kerosene and maybe even ethenol (not methanol though...way too "dirty") it wouldn't run for very long. The soot buildup from burning the fuels would quickly clog the inner workings of the engine and you'd have random cut-outs, engine shut-downs, and possibly even engine seizures. While such an event isn't that major of thing for a vehicle like a tank, you really don't want to have your engine cut out on you while you're flying a helicopter or jet aircraft.
Basically, a jet aircraft could probably only burn through half a tank before the build-up started to take effect.
Also, you'd have to take into account the sheer quantity of fuel that would be needed. I refilled a Sikorsky CH-53 and it took well over 1300 pounds of fuel. Trying to make that much of ethenol would take quite a while. Plus, it would burn through that amount of fuel in about a quarter of the time that it would take to go through a full take of JP4. So the amount of alternative fuels you'd need would be staggering. And, unless you have a death wish, you wouldn't want to fly for very far on anything but the "good stuff".
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