[RPG] Do wands provoke attacks of opportunity

You threaten all squares into which you can make a melee attack, so this usually is not a problem, because melee attacks don't usually get huge reach.

Whenever some element in the game allows you to make AoOs with ranged attacks instead, they usually give you specifics about the working range.
If they don't, you still threaten all squares into which you can make a melee attack, even if you can make it with a ranged weapon, so you probably need some melee weapon that's still useable while you wield the ranged one and that sets your AoO range.

Yes. Say for instance a creature in melee casts a spell that requires a ranged touch attack, it would provoke two attacks of opportunity, one for the casting of the spell and one for the ranged attack in melee.

You still can make only one attack of opportunity for each opportunity that your foe gives you. For example, if you have Combat Reflexes and a Dexterity score of 15 you can make up the three attacks of opportunity each turn. You could make all three of them against the same foe, provided that the foe does three different things that provoke attacks of opportunity. (Link)

While the example from the article doesn't specify the situation I've outlined above it clearly states that though each individual opportunity does not provoke more than once, you can make multiple attacks against a creature provided they offer multiple opportunities.