Just saw this myself, and am wondering about it. I don't follow your analysis Are.
The +2 to Disarm must be a property of the weapon, not the Disarm feature. When doing a Disarm, there is actually a penalty of -4, not a bonus of +2. You only get a bonus of +2 if you have the feat, Improved Disarm. If this weapon granted the Improved Disarm feature, it would probably say so.
As for the reach wording, all I can see is RANGE 10ft for the weapon, and that it grants its wielder reach. The weapon itself does not have the Reach property, so I wouldn't assume that it won't work on adjacent enemies. Also, because it's a light weapon, I can see it working adjacent.
Honestly, I can see the argument from either side, which is why I've asked my DM what he proposes. Maybe the rules have changed since this question was originally posed? I don't know, I'm fairly new to Pathfinder.