You're gonna get better weapons depending on how many enemies you kill per day. For me, the level of the enemy isn't the biggest factor.... it's more like how long you spend looting. If you spend about a half an hour looting at the Thrall Hall (where the highest level enemies are), you won't get as good of loot if you loot for an hour at Raven's Cove. I average killing about 800-1500 enemies per day, and will usually get a Famed or two. Killing that amount of enemies a day will probably get you at least one per day. Of course, sometimes my best loot will come from the first few kills. My best loot has come from the Raven's Cove Mines. I've gotten Blade of the Abyss, Barracuda Blade, Masterwork Broadsword, and Master Crafted Repeater Pistol, to name a few. My second favorite place is the Gold Room on Tormenta, and I go there a lot now (because like you said, Tormenta has way better gold, and I need a lot for my final ship upgrade). Also, sever hopping is another good way to loot. If you've been looting for a bit, and haven't gotten any skulls, then pick a new server to loot on. And an answer to your last question, you can only find Famed Cursed Blades on Raven's Cove or on Isla Tormenta, but you can find regular Famed anywhere... although some are more common in other places.
Also, another tip... a lot of people (including myself) use a good way of looting called running laps, or circling, in Cursed Caverns.
Following this route is a very nice way to loot.