I had heard our galaxy's super massive black hole was a small percentage of the overall mass, but I didn't know it was that small. That's amazing, considering it's over 4 million times the mass of our sun.

Another way to look at it, also, is that the matter in accretion disks around black holes is slowing down and spiraling in due to friction. We ain't! We're content to just keep orbiting way out here in the galactic boondocks, at least until we collide with the Andromeda galaxy in 5 billion years.

That's interesting, I've never heard it put that way. All of the stars in our galaxy are bound to each other via gravity. And they would have similar magnetic fields if they are all rotating the same direction (adding together and making a cumulative magnetic field, similar to two waves in the ocean combining to make one big wave). But over long distances, gravity is much more powerful than electromagnetism. So the force of gravity wins out on large objects like planets and stars. But the galactic magnetic field would definitely have an effect on individual electrons or ions floating around in space, perhaps funneling them towards a certain point, the same way Earth's aurorae funnel solar wind towards the North and South poles.

That's how I understand it, as well. And when it does go Supernova, it's too far away to do serious damage to Earth. It will give off enough light to be as bright as a half moon for about a month. It will even be visible during daylight, but the blast wave will dissipate to almost nothing by the time it reaches us. We'll just have really nice aurorae for a few years as the stellar remains wash over our Solar System (centuries after we see the Supernova itself, since what's left of the star will be traveling below the speed of light).

Not true. Most stars aren't massive enough to go Supernova. Like our sun, they will swell to become red giants, slowly lose their outer material, and shrink to become white dwarves.