Really, I think you'd better try any antenna on the roof, and at varying heights, before you drop a lot of money on a big, sensitive antenna. Your report says reception should be ridiculously easy. What I get from it is that you have 26 stations LOS at 158+/-3 degrees that are all 30 dB or higher NM. I would definitely want KUHT 8 PBS, and the ANT751 should pick that up. Even the UHF arrays should pick that up, though it's out-of-band for them ... it's 61.8 dB! If you went bigger, any of the HBU series from Antennacraft
http://www.antennacraft.net/Antennas/AntennasHBU.html larger than the HBU11 should produce tuner-overload levels of signal.
That brings up another point - is your indoor antenna amplified? You may have so much signal that the voltage coming out of the amp is clipped or your tuner is overloaded. The TV signal at your home should be very strong.
Did you look at the tree pictures on the HDTV primer? If you have a UHF signal and the tree blockage reduces the UHF signal by 90% as shown in the picture, that's still more than 20 dB noise margin for most of these stations. So it it is obstruction by trees that's the problem, getting up where you get some diffraction over the tops of the trees and are in the less dense part of the upper foliage should still provide plenty of signal. And channel 8 is VHF high, and should come in strong, despite the trees... considering how strong it is to begin with.
Are any of your neighbors getting TV OTA? Might be worthwhile to ask around.
If you want, you can get the ANT751 at Walmart, take it on your roof and try it out. If it does not work for you, you can take it back. I have no personal experience with that antenna, but it's often recommended for its capability in a small package, and build quality. So I think it's a safe bet. Any of the Antennas Direct or Antennacraft antennas should work for you, too.
