Could his 2nd attack from his special be activated from dropping a hammer via free action drop? Ex. He's got two tokens, drops a hammer, quakes, successfully hits +3 defense. Could he then make the second attack from his special?

*Can't quote the power, I'm on my phone*

Quake is an attack so if you roll 3+ over you get the free attack.

Quake can have multiple targets so I'm not sure if you'd have to get 3+ against all targets or just one to make it work.

Unless one of the characters ignores knockback or is against a wall or another character you won't have any targets after a quake though.