That looks awesome.
(And I love your working title )
I think the week thing... I mean, if you stop something that's moving (just tried it with an old baby toy with a spinning ball on top) suddenly, it jerks.
If you put your finger on something to stop it slowly (like one of those pinwheel toys) it stops in a series of jerks.
No big deal if what you're messing with is a toy... what's a little shaking?
But picture that planet grinding to a stop... you're shaking the world.
So each time you shake it, buildings will fall, or tidal waves or tsunamis or... whatever.
Well we can survive a disaster. And another right after... well, lots of dead, but people are resourceful, right? And then another and another and another and another ...
yeah after too many of those in one short time frame, might be no one would survive. I can see how "suddenly" might have to be reeeeaaaally sudden.
I can also see how, if the stop was really gradual, like hundreds of years, it would be survivable then too...
Of course this is all me "supposing" and playing with baby toys, so...