Yes yes - we all knew that Jellal was going to be saved by lazy writing. lol That's Mashima for you. He's been doing that for quite a long time now in almost every arc he's written.
And I thought the ex-chairman was going to do something to get the key without killing Jellal. Didn't think he would be stupid enough to transfer it to himself. He's a backstabbing villain himself, so I thought he would at least know that Tartaros would also stab him in the back at first chance.
And my gut feeling is that Elfman would somehow be stopped by Cana, though I'm not sure how. Since the influence placed on him is a "curse" rather than a typical spell, not sure if even Levi or Fried would be able to undo this. And I will stab someone or stab myself if the "power of friendship" makes him "wake up" and stop the blast.
BUT then again, Mashima DID let Phantom Lord destroy the Fairy Tail HQ, he DID let the Etherion fire during the Tower arc, and he DID let the main cast of Fairy Tail completely disappear for 7 years before making a comeback.
So it's also possible he will let Elfman blow up Fairy Tail, but still allow all of them to survive and make a comeback:
I.E. Elfman blows up Fairy Tail and knocks out everyone except Cana and himself, since Cana saw it coming. Cana beats some sense into Elfman and wakes him up. They help Guild and regroup for a counter attack.
Oh, and FACE was bound to be released according to Mashima's patterns. He did let Etherion fire, he DID allow at least some dragons to pass through during the Grand Tournament in the last arc, and he DID let all the council chairmen and many of the ex-chairmen get killed by Tartaros so we all saw it coming - FACE would be activated to advance the plot.