We can't pinpoint the exact point, but we can set a cut-off

You can't set a cut-off with the amount of info available, you can only reduce the chance of killing someone

I think you'd agree that 100% of reasonable consciousness definitions fail under these conditions.

of mind is a long running study that made little progress, 100% is way too confident, I'd personally grant 98.5%+, mere disagreement by experts which would be academic philosophers should reduce your confidence, it shouldn't be 100%, there are a billion theories of consciousness, all untestable

you wouldn't have an issue with a 1 week abortion for example

I wouldn't have a issue for a different reason than it not risking killing anything/anyone, it'd be between certain pain/cost of going through pregnancy vs that very very small probability of killing someone which makes the one a more morally right moral choice without taking 100% certain position on whether or not 1 week old fetus can be murdered.