1) the ap arned in batlles is divided among all the characters used in that battle, if only 1 participated he get all the points

2)Yes, winning 3 tournamnets (not sure...) gives you a special item needed to upgrade a celestial weapon.

3)i think that weapons damage depend of the abilities, remember that abilities like "Damage+3%" increase the damage (no s... !), and if you atack for example a fire fiend with a weapon with the ice ability the damage will be greater.

4) sorry i dont know much about exploits...... but i think that tonberry its found at omega ruins, and to get there you need the airship, and to get the airship.... you need more playing time.

5) weapons with the capture ability are in the monster arena, to get there you need to reach the calm lands (where you do the chocobo training), monster arena is at the right of the map.

Hope this help.