Hi,
To be true I didn'd go through each word in this thread.
What I am missing: There is a requirement for "low phase shift" ...but I don't see any specification.
And I can't find the information what the signal is used for...
Without a value you may discuss a long time and never get to an end.
****
Zero cross.
I'm designing high precision phase control for the industry. And I use zero cross circuits to align the firing angle oir the SCRs.
I found out, that the "phase shift" is a minor problem for a precise regulation.
There are other, like
* timing jitter caused by overtones / distortion of the input (mains) signal
* multiple zerocross trasitions
* voltage fluctuations of mains, causing output signal fluctuations (even with precise phase)
Klaus