1 - Dunno :( Sorry, I don't use it.
2 - What he said. Just wanted to add though. Some fish are sellabel to merchants. Like, in the Forest Ruins are an array of fish and a Troubling of Deep Lurkers. The array will give you frogs, sunfish, and flounder. The deep lurkers will give you average deep lurkers, or something. I have yet to see a tradeskill using them, so I sell them to merchants, for like 13cp each. Not much, I know. But 8 of those and you have a sp. Wouldn't make that my primary sourse of income, but, if you happen to pass by some while killing mobs...
3 - What he said... Seriously, quests. A lot ask you to kill things. You get a reward, and mob drops. Sell anything you don't need, and if you thinks others will, sell it to players. Things that are harvest from the ?s, for example, usually sell for about a silver on Blackburrow. More if they are rare/in demand.