2) Neither mob is very abundant and the Captains are far back in the caves. When you have any amount of treasure chests go back to Randolf
3) Randolf rewards you with 400a per chest and a basic bonus of 19,800a starting from the first one. Although he didn't mention it earlier, apparently you can take the chests to Collob and he can open them too. When I turned in just one item I got 20,200 adena, 6 was 22,200.
4) You can also take the chests to Collob over by the Jewelry and Armor Shops. He will charge you 600 adena to open each chest and says you may get cursed in the process. I opened 3 chests and no curse but I got thread, thread, and cord and at 600 a pop that's not very good.
Here a list of the things that can be in a chest that doesn't curse you:
1 Braided Hemp
1 Animal Bone
1 Scroll Enchantment Weapon D
1 Scroll Enchantment Armor C
And here is what can be in a chest that curses you:
1 Moonstone Earring C
1 Aquastone Ring C
1 Scroll Enchantment Weapon C
1 Stone of Purity
You can get rid of the curse by obtaining at least one more chest from the Pirate Zombies or their Captains.