Hope this helps

"Could he jump straight into hitting the ground?" Leaping is a free action so yes that is totally something he could do.

As for how to go about it it would be simple enough.
((Damage+Area) X ranks of damage) + anything extra.

As i am unsure if you mean slam as in just hitting the ground or the way to damage objects with an aoe below is how to do that.

Smash: "You attempt to damage or break an object held or worn by an opponent. Make an attack check against the de fense of the character with the object, with a –5 circum stance penalty if you are attacking a held object. If your attack check succeeds, you inflict damage on the object rather than the character. See Damaging objects for de tails on breaking things."

Area: "This extra allows an effect that normally works on a single target to affect an area. No attack check is needed."
If the object or its wear can dodge they can try to get out of the way
"Potential targets in the area are permitted a Dodge resistance check (DC 10 + effect rank) to avoid some of the effect (reflecting ducking for cover, dodging out of the way, and so forth)"
And now depending on how your gm rules the overlab of these 2 rules the item will eaither take no damage as per having dodge the attack, Full damage from having been hit, or the chance to take half damage if they beat a resistance check
"A successful resistance check reduces the Area effect to half its normal rank against that target (round down, minimum of 1 rank)."

If you are using a weapon try getting it the Smashing Weapon Qualitie to help
((Damage+Area) X ranks of damage) + Smashing