I think it's the other way with heli engines, more RPM and less torque. It's common for 3D heli pilots to run their engines 17,000 RPM in flight.

As for the other questions, if you can imagine it, it's probably been done given how long glow engines have been around. That doesn't mean though there still isn't room for innovation, especially with the recent advances in hobby grade microprocessors. The big problem with fuel injection though isn't the sensors or the ECU or even the weight and complexity that such a system would add. It's the tiny orifice of the injector itself and the tight tolerances of the pump and regulator that a fuel injection system uses. Alcohol and nitromethane won't cause any problems, but the castor oil in our fuel turns to varnish pretty quickly. A carburetor spraybar can handle quite a bit of it, but a fuel injection system can't.