This is the insides of the service module. I don't see much in the line of fuel.
They don't need a lot. The SPS engine only burns for a few minutes.
Two of the four fuel tanks are sketched in outline in that drawing so you can see the helium tanks behind them. The arrow labeled FUEL STORAGE TANK points near the bottom of one, FUEL SUMP TANK points at the bottom of the other. There are two more like them on the other side.
Here's a another interior view. The two large cylinders are the SPS fuel tanks.

So, you are saying that once it leaves the moon the inertia will carry it 238,900 mi. to earth
Essentially, yes. The engine doesn't need to fire continuously to keep moving. In fact, it speeds up as it approaches closer and closer to earth. It's falling toward earth, remember?
and how do they steer this thing towards earth?
If they start out in the correct trajectory, they will arrive at the desired point. This is accomplished by burning the SPS for the correct amount of time in the correct direction at the proper place in the orbit around the Moon. Errors in the initial trajectory are adjusted by making midcourse corrections along the way - generally short burns in a calculated direction at a calculated spot.
It doesn't show any rockets to steer it by.

Yeah it does. Each RCS Quad has four small rockets (hence "quad"), and there are four of these quads [IIRC] spaced evenly around the outside of the SM that are used to orient the craft in space by firing in specific directions in combinations.
Careful design, planning, and execution. They had very good rocket scientists and aerospace engineers working on it, and a well-trained crew aboard.
But what keeps it from wobbling when it enters earth's atmosphere. It stays at the perfect angle as it is coming in
There's a whole branch of aerodynamics called "blunt body dynamics" that has the answers to this question. Apparently a body shaped like this will tend to remain oriented flat side first, but this is far from my field of expertise. You're the aerospace guy. Look it up and you tell us.
and the shield is hot enough to melt butter and then it deploys parachutes for a soft landing in the water and then it deploys a tubular life raft around the thing to keep it from sinking. Like this picture shows.

My question is, where do they keep this inflatable raft so it doesn't get burned up? You can see it is attached right at the part that is going to get pretty darn hot.
Presumably behind the heat shield which, IIRC, is jettisoned after the parachutes open. You're good at Google. I'm sure you can find it.