If you have 20 ft of tower and 10 ft of mast, why did you enter 15 ft AGL for your tvfool report? You need all the height you can get for your plan, especially with trees. Here is your report at 30 ft for your estimated location:
http://www.tvfool.com/?option=com_wr...f1f0febab36d07
and at 50 ft:
http://www.tvfool.com/?option=com_wr...f1f056e6796d1a
You have some strong FM signals that might cause a problem for your preamp. See the second attachment.