...But our solar system is shown on the scale as being microscopically small compared to the star (in fact, one of the things alleged to have been exclipsed by the larger stars was an entire nebula). That puts the star on a scale that well competes with the size of a galaxy.

They were showing you the planets of our solar system and our sun without the distance of space between them.  Canis Majoris is bigger than all of our planets and our sun combined, however it's not as large as the Milky Way Galaxy (afaik).

The nebula shown is the Eta Carina Nebula - named for the large star there. I think it was meant to scale the star, not the nebula. Reading about these very large stars, I'm certain it's about the star and not the nebula, because appearance these large fellers are at the edge of stellar workability, and larger masses would mean the gass pressures would be sufficient to overpower thier gravity, making for a kaboom. Stars the size of galaxies are just plain impossible.

And Phil Plait is the Bad Astronomer and president of the JREF. A very freindly and accessible kind of guy.

You are also confusing the term nebula with galaxy. A nebula is a generic term for a faint fuzzy bit in the sky. So all galaxies are nebulae but not the other way around. If you look through even the better of affordable telescopes (ie the price is south of $2,000), all that you will ever see is a faint bit of fuzz when you look at any nebula. All the great pictures that you see are taken with hours long exposures (sometimes over several nights) and in a few cases, they even have to be assembled mosaics because even at the lowest useful magnification that a a 'scope may be capable of, the nebula may be too big to fit in a single frame.

Just for fun, if you are in the northern hemisphere and you have clear dark skies tonight, I can direct you to a couple that are naked eye visible if you know how to find them. We will start a couple of hours after it gets dark and find the moon as a reference point.

Look about ten lunar diameters to the right of the moon and one lunar diameter up. If you are lucky enough to have really dark skies and clear still air, you might see a tiny little bit of fuzz perhaps a tenth of the diameter of the full moon.

If you do then congratulations, you are looking at Messier object #31, the most distant object visible to the naked eye. It is also known as the Andromeda galaxy. Even a good set of binoculars will make the viewing better but it will still be a faint fuzzy patch of light. However, it is so distant that all that you will ever see is the hot dense core of the galaxy. If you were to make a composite photograph of the galaxy with the moon in view, you would realize that it is really about 8x the diameter of the moon. As it happens, that is an existing photograph and you can see it here:

http://antwrp.gsfc.nasa.gov/apod/ap061228.html

Our next naked eye nebula is to the left of the moon about twice as far. Look for the constellation of Orion and find the asterism known as the belt. Now look below the center star just about where the great hunter's family jewels should be hanging. Here we have M42 which is a cloud of dust and gas about 24 light years across.

Normally, dust and gas would not look like anything. Most such pockets are dark spots in the sky that block your view of what is behind them. However, this is very special dust and gas. As it happens, M42 is a stellar nursery, which means that the dust and gas are at just the right density that every so often, a small knot of it will undergo gravitational collapse and form a new star. So the cloud is lit up from within by hot young stars.

As far as the nebula in the video, that is Eta Carenae and it is much cooler if you don't just let it just whip past you. It is in the class known as planetary nebulae (which has nothing to do with planets BTW) and more specifically, it is getting ready to go supernova.

If you take a look at better still photographs of it, you can see that the nebula is composed of two giant farts of star stuff ejected from it's poles and that is surrounded by a larger cloud which was the outer layer of the star being blown of in a precursor nova a few thousand years earlier.  Also, a more accurate figure for it's size would be about a couple of thousand AUs across.

It's several billion years old, though it probably hasn't been this voluminous for more than a few dozen million years.  Addressing the issue of a "concentration of matter in space", keep in mind that while Canis is much larger and more massive than our sun, it's also less dense, being spread out as it is to around 2000 solar radii.  I can't find an estimate for the stellar mass of Canis, but it should be well upward of 70 solar masses, which while uncommon, is not unheard of by any means.  One of these days, it will start fusing iron in its core and supernova.