Ignition options clarification

[daniel505gti]

I have been trying to get My mega squirt v3 running only ignition to give stable ignition.
I have a few questions that I can't find answers for.

Predictor algorithm There is no explanation of the differences.
I have found that last interval is the best for me but my hall effect sensor chopper plate has longer metal spaces than air gaps .. Does this effect the default algorithm (first hi second low) or which is the best to use?

Is there a need for next cylinder spark if the trigger is 40 degrees?.. surely the extra time only enables greater chance of errors, or is this needed for calculation time?.

I am organizing a cro to analyze the inputs and see why i get deviation of advance of 5 degrees at certain revolutions.
I have turned off all advance and dwell adjustments to 0 to remove these as passable influences.

any ideas of where else I can look?.