I think part of the problem is that, like many, MANY things in this series, the situation with the 144,000 souls is being presented to us in a "backwards" (or otherwise obfuscated) way.
For example, perhaps it's less that the No-God requires there only to be 144,000 souls on Earwa in order to achieve the Apocalypse -- rather, that is simply how many people will be left once the Apocalypse occurs. The Consult may not even know how many must die, but only that the end-result will be that number. Which would make (some) sense of their "burn it all" methodology. I'm sure there's a mathematical term for this sort of thing but I am a mathematical moron to the highest (lowest?) degree, so...
On the other hand, the number of 144,000 may not be important at all to actually achieving the Apocalypse, so much as it is the number of souls required to repopulate the New World -- once the No-God, or New God, has achieved dominion over the existing one. So, for the Consult it's equally an important number to be reached as it is a signal to stop being genocidal lunatics.
Yes, like a tipping point, just kill until there are only 144k souls left, then it kind of unfolds as it should. In that scenario it would pay to be as far from Golgotterath as possible. I wonder what the rest of Eänna is thinking about the Great Ordeal, the must have heard of it.
The only thing ever said about 144,000 souls in the books is by the Wracu Akka faces off with. That is the number the population has to be reduced to to shut Eärwa off from the Outside. The No-God's is the Consults tool to do this quicker. Once the No-God rises there are no more births. So, many have speculated as to why the No-God even went to war in the first place. They could have waited until people died off and with no more babies being born it wouldn't have taking very long.
not being able to give birth will unite humanity like nothing else. In 5-10 years a new ordeal could be raised with anyone with the mark being trained in sorcery, with humanity's blessing. The consult has to fight anyways.
Or maybe the no god has to war, maybe its part of its code. The no god doesn't seem to have a soul; perhaps it has no choice, no free will either.