If you flip the engine forwards and runs backwards, there is an easy solution I've used.

Flip the engine backwards, it will kick and run forwards. Really.

As for no duel rates on rudder, it's just the choice of the designer of that radio. If you go up a bit in radio complexity, you'll find most do have duel rates on rudder as well. My radio has duel rates and expo on aileron, elevator, and rudder. Some radios have expo on throttle as well.