RE: RMS oddity?

No magic about it. For a *sinusoidal* waveform, the ratio of peak to peak amplitude to RMS is the square root of 2 i.e: 1.41. Your 1.53 is probably due to measurement error or an offset on your waveform. If your input is always going to have the same waveform, then you can use this method. However, if you start putting square waves etc into your circuit, it will give large errors.

Then I wonder why I would need to do a peak to rms type factor when my whole objective is to measure a peak to peak signal and calculate the rms...all I'm seeming to do is attempt to calculate RMS, fail at that, and just multiply the measurement by close to 0.707 and say that's the RMS...which seems redundantly not what I would like.

So I don't know where my error source could be and why it is a nonlinear error. I don't think it could be from rounding in the division and square rooting but maybe I'll look at it in the distant future. For now I'll hide the tweak from my flow charts.