Correct, you want a Fade Margin of at least 10 dB because OTA signals constantly vary in strength.
Yes, antenna gain can be directly added to make the NM more positive. You can also add the amp gain but must subtract the amp Noise Figure which reduces the signal SNR. You might wonder why would you want to do that if it reduces the SNR of the signal coming from the antenna? The answer is that a preamp reduces the total System Noise Figure making the distribution losses minimal and making it possible to receive signals that are about 5 dB weaker because it makes the tuner noise figure irrelevant.

This website compares antennas, but it is a little out of date. Use the net gain figures.

http://www.hdtvprimer.com/antennas/comparing.html

http://www.winegard.com/kbase/uploads/HD7694P.pdf

I don't know. Why don't you call them and ask them. They have been making antennas for a long time, so I assume they know about Florida, and have designed for that.

You do not need to remember details. There are data sheets, you can read reviews on Amazon, and you can google an antenna for more discussion. There is a lot of debate over which antenna is best, but general consensus on which antennas are good for a specific situation. I don't think many would argue against coupling a DB8e or a 91XG with a 30-2476 for fringe viewing where vhf and uhf stations are in different locations, for instance. I don't think anyone would argue against one of the Winegard combo antennas for your situation.

Would like to thank everyone, the recommendation for HD7694P was spot on!

The 8.1 channel (NBC), the one I was having most problems with (despite it being most solid when I was trying my first antenna, an omnidirectional) is now solid, and stays up even during storms, whereas previously with HDX4 I would get complete loss of signal or extreme pixellating!

Without amplifier, I get something like 20 or so channels, and with it I get 55+.

I haven't actually tried watching the major networks (NBC, CBS, FOX, ABC) for extended periods of times without amplifier. But it seems to be okay with amplifier, and would like to keep using it, particularly since I get more channels with it.

What does the symptoms of an overloaded tuner look like, exactly? (for my future reference so I know what to watch for).

Once again. thanks rabbit for the antenna recommendation! Seems stable enough that I've went ahead and ordered a OTA DVR for our house!

Thanks for the good news; glad you like the reception results.
You will usually see pixelation of the weakest signals first.

The strongest signals create spurious signals from IMD (Intermodulation Distortion) that raise the noise floor and reduce the SNR of the weakest signals to less than the minimum required 15 dB.

Here is a spectrum analyzer display of the Antennas Direct Eclipse antenna in a strong signal area without a preamp:

http://forum.tvfool.com/attachment.p...1&d=1472395586

Here is the signal display when an overloaded Mohu Jolt amp has been added:

http://forum.tvfool.com/attachment.p...1&d=1472395586