Make the flaming wither skulls breakable.

For example if the player shoots one, it would have a chance blow up without hitting the floor and there could be particles when it blows up. If it makes any sounds when it is broken, it should make a shattering sound.

Destroy them with an arrow.

I don't quite understand this. Do you want to be able to shoot a flaming wither skull or do you want to be able to destroy them?