Wording may need help but that's why this is collaborative.
Basically his Specialty Boomerangs are and exploding one and a sonic one or some other type that would hinder mess up certain special defenses.
The Returning Boomerang is pretty obvious in that if he misses on the initial attack the boomerang has a chance to come back and hit the target on the way back. I added the bonus against huge figures figuring it would be easier for the boomerang to hit such a big target. That line doesn't have to stay there if we don't want it to, but I put it out there for added theme. The d20 roll for this power can also be adjusted as well if need be.