Can I Feedback from a destroyed ship during simultaneous fire?

E.G. Sablegryphon's Murder of Crows list vs the similarly PS 3 Scouts.

I don't see why not. It's something you can do in lieu of an attack, effectively you're using your opportunity to attack to trigger that upgrade.

I don't see why not. A ship's abilities remain active during simultaneous attack.

Yes. The only requirement is getting to the attack phase which you still do with simultaneous fire.