When I did this, I validated each step before moving on. The first thing I did was draw a visualization of a frustum from an object's point of view, then I could move my camera around and look at it. Then I split it into 4 cascades and again draw each frustum split on screen.
Once you have that, then you know that's working and can move on to the orthographic projection step (which I rendered into textures and drew those as quads on the screen to validate those).
And so on...