Some of this has already been covered.

The ignition has a maximum RPM above which it will provide progressively weaker spark or not spark at all. RCEXL doesn't specifically publish this RPM. We do know they run up to 15k just fine. I would bet it can do 18-20k, but haven't tried. As mentioned above fitting the sensor and magnet will take some work and probably a custom sensor mount and smaller than typical magnet. Unless you can get an ignition with a straight plug boot or make one, you won't be able to get the boot onto the plug deep inside the heatsink head.

Gasoline will have much less power than the typical 20-30% nitromethane glow fuel.

The engine will run much hotter on gasoline. What this will do to the ABC piston and liner fit or life is for you to find out. Oil ratio should be similar to the glow fuel being used, or potentially even more. Use a high temp, high viscosity racing oil.

The carb is designed for the above mentioned glow fuel, on gasoline adjustment will be tough. If it has two needles the idle and WOT throttle can be tuned fairly well, but midrange will be rich, probably very rich. A "third" needle is unlikely to help much in this case. It will be very sensitive to needle adjustments. The difference in a car application compared to an airplane for a carb is that the engine will be operating in a wide range of RPM for a given throttle setting such a simple carb has a hard time dealing with that. It works well with glow fuel because it tolerates a very wide range of air fuel mixture. Gasoline is much more critical. The glow carb will likely also be too large for gasoline. With a slide carb it's fairly easy to just limit WOT as long as this doesn't interfere with tuning the needles.