I have a couple saddles on which the top surface has cracked and crazed like dried mud, countless little flakes, all curling up at the edges, separated from one another by shallow cracks. In other words, the surface has turned into something completely different. With something like that, you can use sandpaper to remove the flakes and smooth the underlying surface. Then, I suppose, you can add some kind of coating to put a new, artificial, surface on the leather. I would not bother. When a saddle gets to that point, it is time to put new leather on it.
For what it's worth, I've only seen this on Ideale saddles. I think they put some kind of surface treatment on the leather, which in time destroyed the surface completely. Here, look:
See, it's an Ideale 80! pretty lovely, eh?
Your saddle is not that bad. You have surface cracks, but the surface is still present. Beyond reshaping it, and applying some neatsfoot oil and/or proofide, I don't think it needs much. If you want to put a nice sheen on it, beeswax is pretty safe. There are other things you can try, such as tung oil furniture polish, but I don't know what effect this will have on the surface.
What you have, of course, is a museum piece. I would not ride it under any circumstances, unless you want to put new leather on it anyway (which I'd be happy to do for you). I think this saddle is worth more to you in its present condition than if it were turned into an essentially new saddle.
As for that Ideale in the photos above, well, I made something useful out of it. Here it is with new leather:
