[3.5] Thunderlance spell questions

[Twilight Jack]

The thunderlance spell in the Spell Compendium creates a pretty cool, force-effect melee weapon with a 20-ft. natural reach (so it can be used against adjacent creatures without difficulty). In addition, it allows the spellcaster to substitute his Intelligence or Charisma in place of his Strength for both melee attack and damage rolls. In addition, it has a chance of dispelling any force effect of 3rd-level or lower that it strikes.

A couple of quick questions. I think I know the answers but I'd like confirmation from a few here whose RAW-fu is strong.

#1: It makes the point that the lance may be wielded in one hand or both. Do you get to add 1 1/2 times your Int or Cha bonus to damage when wielding in both hands? As a corollary, what happens if you were to Power Attack while wielding it two-handed?

#2: This is the real question; if this spell is being cast from an item, whose Intelligence or Charisma is used to determine your bonus to hit and damage? I would imagine that the user of the item gets to use his own, since the control of the already created effect is now his alone. The rules about a magic item using only the minimum stat necessary to cast the spell seems only to apply to setting Save DCs, not any other aspects. So if a wizard with an Intelligence of 22 had a bracer that could create a thunderlance x/day, shouldn't she be able to use her own +6 bonus to determine her attack and damage?

[Twilight Jack]

Oh, and since it's a melee weapon for all intents and purposes, it would stand to reason that you automatically threaten all squares within 20-ft. of you, and that you can use the thunderlance to trip, disarm, sunder, etc. Is this correct?