Well, there are other things to consider. How much of the planet's mass was blown out of the gravity well of the remaining bit? How long would it take to re-accreceate? The atmosphere may disperse, but it would 'cling' to the heaviest masses... etc.
Would it be survivable once the situation settled down, and if the planet remains irregular? Possibly, but it's hard to say. That's a LOT of toxic material thrown out and would settle all over the surface, so you're not looking at Class M anymore. But even without that, the whole 'center of gravity' is now changed, the orbit is likely messed up, etc...
But assuming ALL that stablizes, eventually, and you're still in the life belt, and there's enough atmopshere left.. then, sure, though the gravity would be a little wonky near the 'blast line'. All the ocean may be near the destroyed pole, for instance, due to the amount of 'down' we're dealing with.
Wonky, really, no matter what.
