With the engine off take off the air filter and look down the throat off the carb. The carb should be open only by about 1.5mm with the throttle servo in the neutral position.

To fix this problem you may have to look at your throttle linkage. Post a photo of your setup with the servos at the neutral position.

As for the antenna, the only fix to maintain performace of the signal is to buy a replacement antenna. Then solder it on to the appropriate spot on the receiver.

Ryan