Hey, thanks for the advice, Cerek. One good solution for mages is also Silence spell, which has -5 penalty for saves!
Oh, and I also tried running around and hitting the Duergar with sling and it took me 22 bullets to kill him! That includes the ones when I missed.
So I believe I will fight mostly with magic and that is very tricky because when you rest you go back to square 1.
I think the only possible race for FMC is Half-elf.