I think the third ability as phrased is rather misleading. It should either have reminder text "(You can only activate this ability if you control the creature)", or the whole third ability should be something granted to the equipped creature, something like: Equipped creature has "Sacrifice this creature: Attach Demon Claw Carcanet to target creature."

Assuming it's meant to work like that second example, I like the card a lot.

The sacrifice ability is meant to be used by the Carcanet's controller to put it on his or her opponent's creatures, which is why the equip cost is high. It's a (slightly worse) Pacifism that falls off when the creature dies, that way. I can see where that could be confusing to some players, though, and I can also see the benefits of either player being able to put it on his or her opponents' creatures. I'll have to think about which I like better. This version would, indeed, need reminder text.

And by "It's a Pacifism" I just mean it's that type of removal.

They way it works right now, it's basically a Plague Wind: I sacrifice all of your creatures. It needs to be limited somehow.

Nope. See my comment on 23rd July. You can't sacrifice opponents' creatures.