Fatal Push can target any creature, even one with mana value 5 or greater. The creature's mana value is checked only as Fatal Push resolves.

If a creature on the battlefield has {X} in its mana cost, X is considered to be 0.

Revolt abilities don't care why the permanent left the battlefield, who caused it to move, or where it moved to. They're equally satisfied by an artifact you sacrificed to pay a cost, a creature you controlled that was destroyed by Cast Down, or an enchantment you returned to your hand with Cyclonic Rift.

Tokens that leave the battlefield will satisfy a revolt ability.