Hi Ken! Wow, you're really wanting to dive deep into the physics of EM Radiation. It's definitely a fun topic but incredibly abstract, and to be honest it's something I don't completely understand myself.
1. I can't view .mov files from my computer, so I'll need to let someone else answer these points.
2. While EM waves have two components, they aren't individually isolated components. As you can see by some of those nifty animations you found, the E and M waves oscillate in unison. So the wave is actually the entire thing; there aren't two waves that can be modulated individually.
As for your other questions, you're thinking of waves as a one-dimensional entity, and it's frankly hard to NOT do this because all our pictures of sine waves make them look this way. If a sine wave is a one-dimensional representation of a wave, then our analogy of the lake yesterday is a two-dimensional representation. If you take the cross-section of the lake, you'll see that the water forms a sine wave. Two-dimensionally, viewed from above the lake, this happens via concentric circles.
So let's consider a three-dimensional representation. (Have you ever played Final Fantasy X? If so you'll be able to picture this pretty well.) Imagine a huge sphere of water that's suspended in the air. In the center of the sphere is a balloon. It "pulsates" by expanding and contracting, and this pushes waves of water, in all directions at once, to the surface of the sphere. This is how waves work in three dimensions.
Now for the wireless client - imagine another balloon resting on the surface of the sphere. Now imagine that instead of "bobbing" up and down, this balloon expands and contracts like the balloon in the center, so that it's always barely touching the water's surface. As the waves travel outward, they cause that balloon to expand and contract at the exact same FREQUENCY as the balloon in the center of the sphere. The "data" has been replicated on the surface using the waves of the water as a medium.
I caps'd FREQUENCY for a reason there. The frequency of the pulses is perfectly replicated, but the POWER isn't. That balloon in the center is doing some heavy expansion and contraction, but by the time those waves reach the surface, they aren't quite as strong. The POWER of the waves (called the AMPLITUDE) is irrelevant to the "data". As long as the waves were strong enough to move that client balloon, that's all that matters.
So all of this is to answer #3. Waves have what we call "free space loss", which is how much the AMPLITUDE of the waves decreases over distance (without running into anything). The frequency never changes, just the AMPLITUDE. The EM Wave will go on for infinity in free space, but it will eventually fade to the background noise of the universe because the amplitude will become infinitesimal.
Going back to our water sphere, imagine that the sphere is only a few meters wide. We should have no problem seeing those balloons working fine. But now what if the sphere was miles and miles wide? If the water was 100% perfectly calm (and friction was non-existent), and our client balloon was perfectly sensitive to the waves, then it doesn't matter how big the sphere is, the data could be transmitted. However, the odds of the water being perfectly calm are pretty slim, and our balloon isn't going to be perfectly sensitive - it will miss tiny waves that don't have enough force to move it. So the waves will eventually be buried by the "background noise" of the disturbed water, and even if a tiny wave makes it to the surface, our client balloon might not even notice.
Whew, another long post! Let me know if you have any questions about any of this.
Jeff
