The first issue and you have been advised about this before is that the airplane is just too heavy. You can't make a Ballerina out of a pig. Second is the elevator issue. If your TX supports dual elevators then why arent you using it? If you are using a JR or Spektrum TX the flap would be for aileron 2 so that tells me you could be using a Y connector on your ailerons which means that is set up poorly too.