In 2 dimensions, order doesn't matter. But in 3 dimensions, order almost always matters. So make sure you have the order the way you want it. I would take some special cases, easy ones, and just do the rotation in your head to see if they come out right.
Incidentally, your computations in Post # 24 agree with mine. You have successfully computed
which would be (assuming you're always left-multiplying by the matrices) the z rotation followed by the x rotation.