Help me with a paradox
I am familiar with the term “pārisuddhi-sīla”, but this only relates to monastic practice (restraint according to Vinaya, restraint of senses, purification of livelihood and restraint in use of the four requisites). I have not heard of the "ultimate version of the five precepts"... where are these mentioned?

Your first five bullet points are mentioned in the Atthasālinī under courses of immoral action (also mentioned in the Vinaya), but I have not encountered “If you can stop a killing you must stop it”. Is this from a Mahāyāna text?

Your questions seem to be around this final bullet point.

Please help me to better understand and I may be able to offer an answer.