Maybe I've missed something, but I can't find anywhere that the bombs are nuclear...

I can't imagine the king recovering from this anytime soon...if at all. It would be a bit anticlimactic, but the arc was never really about the king, but about Gon and Pitou.

The thing with Komugi being held hostage was kind of predictable, as it would've been the surefire way to force Pitou to obey Gon. Unless she learns of the kings death and decides not to care anymore about Komugi.