Oh dear...what happened to changing Servo.h to ServoTimer2.h?
And you still haven't said if you're seeing the correct 1200 - 1800 values coming through in the receiver. Or what the actual problems are. You may be able to see what's happening but the rest of us can't.
BTW I think I may have spotted a reason for the vibrating...you're writing to the servo every time round the loop even when no command has been received. See if this
void loop() {
while ( HC12.available()>0) {
ROT = HC12.read();
Serial.println(ROT);
myServo.write(ROT);
}
}
is any better.
Steve