Geoffrey and Island of Despair

So, I was talking to Geoffrey after the Black Mountain Mines, and had the option to ask him where the Isle of Despair is. Which is good, but why does he know and no one else? I thought, now that I have the coordinates for the harbour, I don't need Teach anymore and could go and buy my own ship - but no. Speculations?

Also, as an evil character, I killed Gilbert ( and Cedric, two fate points, yay.)..is there a similar npc like him in terms of helping me and telling me what to do, just for the evil side? I am feeling a little left alone, my last playthrough was..8 years ago, and if I remember correctly, Bates always told me what to do. I could not find any evil walkthroughs to help me with that, only hints that the evil way differs much from the good way.
Do I still have to visit the Nasrudin grave as an evil character? And if not, is it still possible for me to buy my own ship?

 

Knowing where the Isle is isn't that unique - most captains know, and use that knowledge to avoid it.

You can't but a boat because no one's selling at the moment. There is a boat under construction in Black Root, but it won't be available for sale until later in the game.

There are evil questgivers along the evil path of the main plot, but that's later on, when Gilbert would no longer be of much help anymore. The ones I'm talking of are two evil elves which are +/- equivalents of two good elves from the good path.

Earlier though, there is no evil equivalent of Bates (which isn't really good to begin with, neutral more like). The plot carries itself though, with or without him. If you don't know what to do and need help, you can keep Virgil around, he usually has a hint. Also, there's a hint on the screenshot in the loading menu.

T'sen-Ang is where the good path and the evil path diverge.

No. You can, but you don't have to.

Unlike when following the good path, you don't have to. But yes, the option is open to you.