Boltzie, click HERE
to view the TV Fool report for my exact location and antenna height. I receive all of the digital stations in the green, yellow and pink fields except for a couple of low power stations. I do not receive any stations in the gray fields unless atmospheric conditions are good (tropospheric ducting).
Yes, you're essentially interpreting the noise margin information correctly. Theoretically, you should be able to add your antenna's gain to the NM figure; however, in actual practice, when you're dealing with weak signals, there is quite a bit of luck involved. For example, WQED is my third strongest Pittsburgh station, but if the TV Fool data is to be belived, WPXI should be stronger, but it is, in fact, weaker. Along with WPGH and WQEX, WQED is near the bottom of the pink field.
Lastly, evaluate antenna mileage claims with skepticism. Most are highly exaggerated for real life situations.