Traxor, looks like you have an ATI and there's some shading problems, right? There's some tweaks in some files for those cards to boost the fps and improve the shadows... Wished I'd find them...
Btw, the keeper is the best boss, the sarge's ok (but they openly tell you how to kill him/it). The final boss is wow, huge, but it's rather easy.
Doom Shotgun powa!!!
Traxor, did you say to needed help to go on?