I can only answer one of the questions since im not really familiar with the others yet since im not in the game yet.
2. With tradeskills, they are used to gain $$$, but can also be a money sink at the same time. Example would be Leathercraft, you choose Skinning as your other profession. You fight some enemys and skin them for some light leather, you use Leathercraft to make a piece of armor. You sell it on the Auction House for 3 silver. Some look at it as a profit of 3 silver, while others will look at how much you could of sold the individual skins for. Its all about playing the market to make some $$$. Another "profit" of tradeskills would be the benefit of outfitting your characters with armor / weapons you have made on your journey.
Gathering professions seem to be more profitable, but once Retail comes, it 2,000 people on a server do Skinning, the profit is gonna drop. All about finding a hole in the market, good luck. Kinda long, hope it helps.