Concrete – What are the options for saving this building

I have a small building on my property that is about 15ft by 10ft. The building sits on a slope that runs downhill sort of at an angle from one front corner to the opposite back corner.

It sits on an odd foundation (at least odd in my experience). The front edge is sitting on a solid-looking concrete footer that is in the ground flush, while the back seems more or less unsupported. The sides of the building rest on some kind of concrete walls. I say "some kind" because it's sort of a chunky looking aggregate, with lots of little round-ish stones in it. Perhaps a home-made mix of some kind? The building has been there since pre-1948. Basically, it's not the smooth, homogenous concrete you'd expect to see poured today.

I say the back seems unsupported because the back wall to the ground is wooden, and doesn't seem solid enough to me to be bearing any real weight. But it could be. All I can say is that I couldn't knock it out with my bare hands.

This image is of the back corner where the separation of the side concrete and back wooden walls is clearly evident. This gap measures about 3.5" at its widest (top), and has probably increased about 2" in the last 2-3 years.

This image is of the other back corner, on the downslope side (meaning the building is leaning downhill toward this corner). Here, there is less separation on this side, but the angle of the side wall is still easy to see.

Both side walls show a pronounced bow front-to-back, and both are severely cracked top-to-bottom. I think is essentially creating extra movement, as the walls are now no longer one solid piece, but really four that can now move separately.

I think the building is getting to the point where it's leaning so badly that it must either be re-seated or torn down. I would like some advice on how you would go about trying to save the building. Or if it's an obvious lost cause.