Thanks for this question, you made me try to remember my high school trigonometry
Please take a look at the attached file which gives you separate controls for the step height and the thickness specified in your diagram by the magenta line. the depth of the steps uses the angle of the spline and the height of the step to create the correct size.
I'm afraid it's not possible to control the height of the step, the depths of the step, and use the spline and still get full size steps. Instead I've given you two modes. In free mode, your dimensions are strictly followed, but the final step may be sliced. In Adaptive mode there may be some subtle scaling to get only whole steps to fit the spline's length.
I hope that helps,