OK, since you liked the new layout, I took some time from my lunch break and found the issue with STF on Ha, cross this bug out.
BTW, how about 4 buttons: "Show Ha Emission", "Show Ha Continuum", "Show RGB", "Show HaRGB" ? When I was using PixelMath for the same process, the image that was giving me better indication that I had the parameters correct was the C(ontinuum) one, not the Ha emission, what do you think?
And if yes, HaContinuum = HaOriginal - HaEmission will do the trick? correct me if I'm wrong please.