A83A

Your original reading was closer to correct. Choose a square within range of your weapon. Then make a ranged basic attack against every target in or adjacent to that square with your weapon. The big difference between your original reading and this one, is there does not need to be a target in the central square.

I could see an alternative reading that would allow a rba against enemies within range+1 of the weapon (not -1), but that seems silly. Given that the ability could be understood either way, I'd go with the first one which makes more sense though.

A83BA

I don't see anywhere saying all attacks must be made with the same weapon, but it does say these must be weapon attacks. So a sorcerer's spells wouldn't count. But I suppose attacking some people with a bow and others with a thrown knife might be do-able. If that were the case, I'd limit the range of the power to the shorter range between any weapons being used though. There's also a possibility of needing something like quickdraw to allow changing weapons mid-attack. I don't know that off the top of my head, and I don't feel like digging in far enough to find that detail when I doubt anyone would really want to do it anyway.