1) It's called "Kinslayer".

*takes off smartass hat*

2) I don't think you can switch in and out of Dark Mode, so no. You'll have to play the whole game in Dark Mode. Which really shouldn't be too much of a problem if you've already made it near the ending on Hard.

Cintrian Pendulum, but part of that is just that it causes the least amount of graphical glitches.

Yeah, the cave where you get the Ostmurk is actually my grinding spot of choice in Act I. You won't get jumped from behind as much, and if you bring some Dancing Stars, you can clean out the cave quickly, run back to just before the waterfall, meditate 24 hours and start over. Just be careful because when you get to the wider part of the cave, about 3 nekkers will have spawned behind you. But otherwise, it's much easier to farm there than in the forest because you generally don't get jumped from behind.

Stay away from those nekker nests until you've leveled up a bit more. If you just run past them, they won't chase you and there's not much point in trying to kill them in those areas because they'll just keep coming before you can pick up the loot.

And I wouldn't worry too much about keeping any items you get from endregas, until you do the Endrega Contract quest, you can farm them pretty easily.

Well consider me looking forward to it, sir.

Anyway, a little more advice on dark mode since I just remembered it myself (the hard way...) - on Iorveth's path particularly, you want to do your grinding for the Kinslayer set in advance before finishing Act II. The next Act is incredibly short on this path, and grinding is a giant pain in the ass. Bring something like... I dunno, 6000 Orens? I totally forgot about this problem, and now I'm stuck in Loc Muinne with no money, running back and forth, killing three gargoyles and four harpies at a time. Ugh.