Be open to trying alternate mounting locations and elevations. Using HDHR signal quality, not strength, as the key measurement, adjust the antenna aim for best results. If the antenna has to aim at the trees, to maximize signal quality, so be it. What happens when you run this test,
http://forum.tvfool.com/showthread.php?t=13646, using the HDHR tuner as the test tuner?
Signal strength at 100 units suggests that you are at risk of overload. Try removing the amplifier from the system all together.
If you can't get acceptable results with the existing antenna, consider stepping up to a Winegard HD7694P or Antennacraft HBU-33.