Graceful Edge, sunblades?

The Graceful Edge feat from Dungeon #128 (the AoW adventure) lets you
pick a one-handed slashing weapon and "If you do not wield a shield or
weapon in your off-hand, you treat your chosen weapon as a light
weapon."

Does wielding a weapon two-handed count as wielding a weapon in your
off-hand, or are they trying to exclude TWF?

Does treating the weapon as light mean that you can't Power Attack with
a longsword (even for -1/+1) if you're using it with Graceful Edge?

The sunblade makes me ask similar questions: "This sword is the size of
a bastard sword. However, a sun blade is wielded as if it were a short
sword with respect to weight and ease of use. (In other words, the
weapon appears to all viewers to be a bastard sword, and deals bastard
sword damage, but the wielder feels and reacts as if the weapon were a
short sword.) Any individual able to use either a bastard sword or a
short sword with proficiency is proficient in the use of a sun blade.
Likewise, Weapon Focus and Weapon Specialization in short sword and
bastard sword apply equally, but the benefits of those feats do not
stack."

Does that mean you cannot Power Attack with a sunblade? Or can you
choose to treat it either as a bastard sword or as a short sword? Or can
you get the best of both worlds, for example using Weapon Finesse, but
getting x1.5 Str to damage and Power Attacking two-handed for -1/+2?

Well, wielding a weapon in two hands means to me there's a weapon in my off-hand that I'm wieldling. So yes.

A light weapon can't be used to PA. Yes.

Sunblade: Trickier. Since you can obviously use it as a bastard sword (feats) IMHO you should be able to PA... While using Weapon Finesse... Duh.

Granted, since you can do the same trick with a spiked chain, it's not too bad. Watch out for the halfling spiked chain fighter with Power Attack.

IMO for Graceful Edge they should have just said what they wanted to say, ie treat the weapon as finessable. And the limitation to no shield/off-hand weapon, while gaining you style points, seems rather unnecessary.